Different-side double-beam welding process

Abstract

A different-side double-beam welding process, comprising: a lapping step of lapping an inner surface of a first metal member on an inner surface of a second metal member; and a welding step of synchronously performing laser heat conduction welding, by using a laser heat conduction welding apparatus, on the outer surface of the first metal member and the outer surface of the second metal member along the same preset welding path.

Description

Opposite side double-beam welding process

[0001] The present application claims priority to a Chinese patent application No. 202410462810.2, filed on April 17, 2024, and entitled "Opposite side double-beam welding process", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of welding process, in particular relates to an opposite side double-beam welding process. BACKGROUND

[0003] Generally, the shell of the soft package battery cell is an aluminum plastic film, and the sealing is usually completed by using ultrasonic or hot pressing process to melt the plastic; however, for the battery shell made of pure aluminum foil or aluminum plate without plastic, the above sealing process cannot be used.

[0004] The thickness of the conventional ordinary aluminum shell is more than 0.5 mm, and the shell has high tolerance to small defects when laser welding is performed. However, when the metal base material has a thickness of 0.3 mm or less, especially when the aluminum foil has a thickness of 0.2 mm or less, the shell thickness is thinner, which makes the welding difficulty increase sharply, and defects such as perforation and undercut are easily formed, and the welding quality is poor. SUMMARY

[0005] The technical problem to be solved by the present application is that the welding difficulty increases sharply for the metal base material with a thickness of 0.3 mm or less, and defects such as perforation and undercut are easily formed, and the welding quality is poor. An opposite side double-beam welding process is provided.

[0006] To solve the above technical problem, the present application provides an opposite side double-beam welding process, which comprises:

[0007] A lap step of lapping the inner surface of the first metal piece on the inner surface of the second metal piece;

[0008] A welding step of simultaneously performing laser heat conduction welding on the outer surface of the first metal piece and the outer surface of the second metal piece along the same preset welding path by using a laser heat conduction welding device.

[0009] Optionally, the process further comprises a pressing step of moving the pressing device along the welding track of the laser heat conduction welding device and simultaneously pressing the welds on the outer surface of the first metal piece and the outer surface of the second metal piece.

[0010] Optionally, the process further comprises a flattening step arranged before the welding step and after the lap step, and the flattening step comprises:

[0011] The first metal piece and the second metal piece after lapping are flattened by using a tool.

[0012] Optionally, the welding step comprises using a set of laser heat conduction welding equipment with a first welding gun and a second welding gun; or, using two sets of laser heat conduction welding equipment, each set of laser heat conduction welding equipment having one welding gun, wherein the welding gun of one set of laser heat conduction welding equipment is the first welding gun, and the welding gun of the other set of laser heat conduction welding equipment is the second welding gun.

[0013] Optionally, the pressing device comprises a first pressing part and a second pressing part, the first pressing part and the first welding gun constitute a first welding group, the first pressing part and the first welding gun are arranged at intervals so that the laser welding point of the first welding gun and the pressing point of the first pressing part are arranged at intervals; the second pressing part and the second welding gun constitute a second welding group, the second pressing part and the second welding gun are arranged at intervals so that the laser welding point of the second welding gun and the pressing point of the second pressing part are arranged at intervals.

[0014] Optionally, the interval between the laser welding point of the first welding gun and the pressing point of the first pressing part is 0-50mm, and the interval between the laser welding point of the second welding gun and the pressing point of the second pressing part is 0-50mm.

[0015] Optionally, the interval between the laser welding point of the first welding gun and the pressing point of the first pressing part satisfies the following relationship:

[0016] Optionally, the interval between the laser welding point of the first welding gun and the pressing point of the first pressing part satisfies the following relationship:

[0017] When the pressing device moves from the pressing point of the first pressing part to the laser welding point of the first welding gun, the temperature of the laser welding point of the first welding gun is more than half of the melting point of the first metal piece.

[0018] Optionally, the interval between the laser welding point of the second welding gun and the pressing point of the second pressing part satisfies the following relationship:

[0019] When the pressing device moves from the pressing point of the second pressing part to the laser welding point of the second welding gun, the temperature of the laser welding point of the second welding gun is more than half of the melting point of the second metal piece.

[0020] Optionally, the welding speed of the first welding gun in the first welding group is the same as the moving speed of the first pressing part of the pressing device; the welding speed of the second welding gun in the second welding group is the same as the moving speed of the second pressing part of the pressing device.

[0021] Optionally, the opposite-side double-beam welding process is used in the processing of a battery, the battery comprising a cover plate, a first metal shell and a second metal shell; the first metal piece in the opposite-side double-beam welding process is the first metal shell or the cover plate, and the second metal piece is the second metal shell.

[0022] Optionally, the first metal shell has a first skirt, and the second metal shell has a second skirt; the first skirt comprises a first sub-skirt and a second sub-skirt connected to the first sub-skirt, and the second skirt comprises a third sub-skirt and a fourth sub-skirt connected to the third sub-skirt; the cover plate is arranged between the second sub-skirt and the fourth sub-skirt; the first sub-skirt constitutes the first metal piece, and the third sub-skirt constitutes the second metal piece; the first sub-skirt and the third sub-skirt are both flat plates.

[0023] The overlapping step comprises overlapping the first sub-skirt on the third sub-skirt, and overlapping the second sub-skirt and the fourth sub-skirt on opposite sides of the cover plate.

[0024] Optionally, the welding step comprises welding of the first sub-skirt and the third sub-skirt, welding of the second sub-skirt and the cover plate, and welding of the fourth sub-skirt and the cover plate.

[0025] According to the hetero-side double-beam welding process of the embodiment of the present application, the laser deep penetration welding is commonly used in the prior art, the laser power density of the laser deep penetration welding is higher than a certain threshold of the base material, a spoon hole is formed, and when ultra-thin plates (especially plates below 0.2 mm) are welded, defects with a risk of leakage are more likely to be formed. However, the embodiment of the present application adopts laser heat conduction welding on both sides of the base material. The laser heat conduction welding refers to that the laser power density is lower than a certain threshold of the base material, so that no spoon hole is formed in the welding process. BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 is a schematic diagram of the overall battery shell of the hetero-side double-beam welding process according to the first embodiment of the present application;

[0027] FIG. 2 is a schematic diagram of the distribution of the welding group of the hetero-side double-beam welding process according to the first embodiment of the present application;

[0028] FIG. 3 is a schematic diagram of the welding surface after welding according to the prior art;

[0029] FIG. 4 is a schematic diagram of the metallography at the position of the dashed line h in FIG. 3;

[0030] FIG. 5 is a schematic diagram of the surface appearance of the hetero-side double-beam welding process according to the first embodiment of the present application;

[0031] FIG. 6 is a schematic diagram of the metallography at the position of the dashed line in FIG. 5;

[0032] FIG. 7 is a schematic diagram of the surface appearance after welding of the control experiment of the present application.

[0033] The reference signs in the specification are as follows: 1, first skirt; 11, first sub-skirt; 12, second sub-skirt; 2, second skirt; 21, third sub-skirt; 22, fourth sub-skirt; 3, welding gun; 4, pressing part; 5, first metal shell; 6, cover plate; 7, second metal shell. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0035] First embodiment

[0036] As shown in FIG. 1, one of the application scenarios of the embodiments of the present application is as follows: the battery shell includes a first metal shell 5 and a second metal shell 7, one of the first metal shell 5 and the second metal shell 7 is provided with a containing cavity, and an electric core is placed in the containing cavity. More specifically, the first metal shell 5 is provided with a containing cavity, and the second metal shell 7 is not provided with a containing cavity. The second metal shell 7 is a flat plate, and the first metal shell 5 and the second metal shell 7 can surround an inner cavity for placing an electric core. A first skirt 1 extends around the first metal shell 5, and a second skirt 2 extends around the second metal shell 7. The first skirt 1 includes a first sub-skirt 11 and a second sub-skirt 12. In this embodiment, two first sub-skirts 11 are provided and are both flat plates. The second sub-skirt 12 is arc-shaped, one side of the second sub-skirt 12 is connected to one of the first sub-skirts 11, and the other side of the second sub-skirt 12 is connected to the other first sub-skirt 11. The second skirt 2 is a flat plate, and the second skirt 2 is integrally formed with the second metal shell 7. The second skirt 2 in this embodiment includes a third sub-skirt 21 and a fourth sub-skirt 22. The third sub-skirt 21 is oppositely arranged with the first sub-skirt 11, and the fourth sub-skirt 22 is oppositely arranged with the second sub-skirt 12. The two sides of the fourth sub-skirt 22 are connected to the third sub-skirt 21, and the third sub-skirt 21 and the fourth sub-skirt 22 are flat plates. The first skirt 1 and the second skirt 2 can surround a recessed cavity for placing a cover plate 6. The cover plate 6 is placed in the recessed cavity and electrically connected with the electric core in the containing cavity. The thicknesses of the first skirt 1, the first metal shell 5, the second metal shell 7 and the second skirt 2 in this embodiment are all 0.2 mm, and the materials of the first skirt 1, the first metal shell 5, the second metal shell 7 and the second skirt 2 are all pure aluminum materials. The thickness of the cover plate 6 is greater than 0.3 mm, and the cover plate 6 is a metal material.

[0037] The hetero-side double-beam welding process provided by the first embodiment of the present application includes a lap step and a welding step. The lap step is as follows: the inner surface of a first metal piece is lapped on the inner surface of a second metal piece. In this embodiment, the first metal piece is the first sub-skirt 11, and the second metal piece is the second sub-skirt 12. The welding step is as follows: a laser heat conduction welding device is used to simultaneously perform laser heat conduction welding from the outer surface of the first metal piece and the outer surface of the second metal piece along the same preset welding path.

[0038] The welding method of the embodiment is different from the prior art. In the prior art, laser deep penetration welding is commonly used. The laser power density of laser deep penetration welding is higher than a certain threshold of the base material, and a keyhole is formed on the base material. However, in the embodiment, laser heat conduction welding is used. Laser heat conduction welding refers to a welding method in which the laser power density is lower than a certain threshold of the base material, so that no keyhole is formed during welding.

[0039] Furthermore, in the embodiment, laser heat conduction welding is performed simultaneously from the outer surface of the first metal piece and the outer surface of the second metal piece. The first metal piece and the second metal piece are heated and melted simultaneously from the respective outer surfaces. Since the first metal piece and the second metal piece are welded synchronously, the laser beams emitted by the two welding guns 3 coincide at the same point and heat simultaneously from opposite directions, which accelerates the welding speed and ensures that the first metal piece and the second metal piece are melted simultaneously, thereby better achieving the effect of fusion of the two pieces and improving the welding quality.

[0040] As can be seen from the above, the heterolateral double-beam welding process of the present application performs laser heat conduction welding on opposite sides of the base material, and a welding point is naturally formed on the two surfaces of the base material. The welding point is formed by laser irradiation.

[0041] In other embodiments, the first metal piece and the second metal piece can be metals of different materials, and the thicknesses of the two pieces can also be different. Therefore, the material and thickness of the first metal piece affect its welding power. The material and thickness of the second metal piece affect its welding power.

[0042] In the embodiment, the heterolateral double-beam welding process further includes a flattening step arranged before the welding step and after the lapping step. The flattening step includes flattening the first sub-skirt edge 11 and the third sub-skirt edge 21 after lapping by using a tool. That is, after lapping, the first sub-skirt edge 11 and the third sub-skirt edge 21 are flattened by using an external tool, so that the first sub-skirt edge 11 and the third sub-skirt edge 21 are completely attached.

[0043] In the embodiment, an assembling step is further included, which is arranged before the lapping step. At least one of the first metal shell 5 and the second metal shell 7 is provided with a receiving cavity, and the battery cell is placed in the receiving cavity. In the embodiment, the battery cell is placed in the first metal shell 5 and the second metal shell 7 before the lapping step. After the welding is completed, the battery cell is sealed and closed in the first metal shell 5 and the second metal shell 7.

[0044] The lapping step includes lapping the first sub-skirt edge 11 on the third sub-skirt edge 21, and lapping the second sub-skirt edge 12 and the fourth sub-skirt edge 22 on opposite sides of the cover plate 6.

[0045] In the embodiment, a set of laser heat conduction welding equipment with the first welding torch 3 and the second welding torch 3 is adopted; alternatively, two sets of laser heat conduction welding equipment can also be adopted, each of which has one welding torch 3, wherein the welding torch 3 of one set of laser heat conduction welding equipment is the first welding torch 3, and the welding torch 3 of the other set of laser heat conduction welding equipment is the second welding torch 3. Regardless of which laser heat conduction welding equipment is adopted, it must satisfy the condition of having the first welding torch 3 and the second welding torch 3.

[0046] The welding step of the embodiment includes welding of the first sub-skirt edge 11 and the third sub-skirt edge 21.

[0047] The welding of the first sub-skirt edge 11 and the third sub-skirt edge 21 includes:

[0048] The first predetermined welding power of the first welding torch 3 and the second predetermined welding power of the second welding torch 3 are selected respectively;

[0049] The first welding speed is selected;

[0050] The first welding torch 3 is close to the first sub-skirt edge 11 in the first sub-skirt edge 11 and the third sub-skirt edge 21 after the lap joint, and the second welding torch 3 is close to the third sub-skirt edge 21 in the first sub-skirt edge 11 and the third sub-skirt edge 21 after the lap joint;

[0051] The first welding torch 3 performs welding from the outer surface of the first sub-skirt edge 11 along the preset welding path at the first welding speed, and the second welding torch 3 performs synchronous welding from the outer surface of the third sub-skirt edge 21 using the same preset welding path and the first welding speed as the first welding torch 3.

[0052] When the thickness and material of the first sub-skirt edge 11 and the third sub-skirt edge 21 are completely the same, the first predetermined welding power and the second predetermined welding power are the same in the embodiment, and since the first sub-skirt edge 11 and the third sub-skirt edge 21 are both flat plates, the preset welding path is also the same. Taking the preset welding path as a straight line as an example in combination with the drawings, the first welding torch 3 and the second welding torch 3 perform welding from the right boundary to the left boundary in the drawing, and the orthographic projection of each laser welding point of the first welding torch 3 and each laser welding point of the second welding torch 3 on the inner surface of the first sub-skirt edge 11 completely coincides, so that the first welding torch 3 and the second welding torch 3 perform bidirectional heating on each position of the base material during the whole welding process.

[0053] In the embodiment, the welding step further includes welding of the second sub-skirt edge 12 and the cover plate 6, and welding of the fourth sub-skirt edge 22 and the cover plate 6; wherein the welding of the second sub-skirt edge 12 and the cover plate 6 includes:

[0054] The third predetermined welding power of the first welding torch 3 is selected;

[0055] The second welding speed is selected;

[0056] selecting a first welding path;

[0057] The first welding torch 3 is close to the second sub-skirt edge 12 after the lap and the second sub-skirt edge 12 in the cover plate 6, and the first welding torch 3 welds from the outer surface of the second sub-skirt edge 12 along the first welding path at the second welding speed;

[0058] The welding of the fourth sub-skirt edge 22 and the cover plate 6 includes:

[0059] selecting a fourth predetermined welding power of the second welding torch 3;

[0060] selecting a third welding speed;

[0061] selecting a second welding path;

[0062] The second welding torch 3 is close to the fourth sub-skirt edge 22 after the lap and the fourth sub-skirt edge 22 in the cover plate 6, and the second welding torch 3 welds from the outer surface of the fourth sub-skirt edge 22 along the second welding path and at the third welding speed, so that the first welding torch 3 and the second welding torch 3 are synchronously welded.

[0063] The second welding path is coincident with the orthographic projection of the first welding path on the inner surface of the first sub-skirt edge 11.

[0064] In the embodiment, the welding of the second sub-skirt edge 12 and the cover plate 6 is to weld the second sub-skirt edge 12 and the cover plate 6 into one body, and at the same time, the fourth sub-skirt edge 22 is welded and the cover plate 6 is welded into one body, so that the cover plate 6, the first skirt edge 1 and the second skirt edge 2 form one whole.

[0065] It is worth noting that, since the thickness and material of the second sub-skirt edge 12 and the fourth sub-skirt edge 22 are the same in the embodiment, and are welded at the same time on the same cover plate 6, the third predetermined welding power and the fourth predetermined welding power are the same in the embodiment.

[0066] However, due to the different structures of the second sub-skirt 12 and the fourth sub-skirt 22, i.e., the second sub-skirt 12 is arc-shaped and the fourth sub-skirt 22 is flat-shaped, in the perspective of the inner surface of the first sub-skirt 11 (in other words, in the perspective of the top view of Fig. 1 viewed from top to bottom), both the first welding path and the second welding path are straight lines. However, in fact, the first welding path needs to follow the surface of the second sub-skirt 12, and the welding path is a straight line in the perspective of the inner surface of the first sub-skirt 11, but is an arc line in the perspective of the inner surface of the first sub-skirt 11 (i.e., in the perspective of the front view of Fig. 1). The second welding path needs to follow the outer surface of the fourth sub-skirt 22, and is a straight line in both the perspective of the inner surface of the first sub-skirt 11 and the perspective of the inner surface of the first sub-skirt 11. Therefore, the second welding speed and the third welding speed in the embodiment can be different. However, the second welding speed and the third welding speed need to satisfy that the laser welding points of the second sub-skirt 12 and the laser welding points of the fourth sub-skirt 22 are coincident in the orthographic projection on the first sub-skirt 11, so that the first welding torch 3 and the second welding torch 3 also synchronously weld.

[0067] In the embodiment, the pressing device includes the first pressing part 4 and the second pressing part 4, the first pressing part 4 and the first welding torch 3 constitute a first welding group, the first pressing part 4 and the first welding torch 3 are arranged at intervals, so that the laser welding point of the first welding torch 3 and the pressing point of the first pressing part 4 are arranged at intervals; the second pressing part 4 and the second welding torch 3 constitute a second welding group, the second pressing part 4 and the second welding torch 3 are arranged at intervals and so that the laser welding point of the second welding torch 3 and the pressing point of the second pressing part 4 are arranged at intervals; the first welding group is arranged on the outer surface of the first skirt 1, and the second welding group is arranged on the outer surface of the second skirt 2, so that the first pressing part 4 and the second pressing part 4 are oppositely arranged to sandwich the first skirt 1 and the second skirt 2 after the lap joint step is completed.

[0068] The pressing step includes:

[0069] Installation: placing the first pressing part 4 on the outer surface of the first skirt 1 and placing the second pressing part 4 on the outer surface of the second skirt 2;

[0070] Parameter setting: selecting the pressing degree of the first pressing part 4; adjusting the position interval between the laser welding point of the first welding torch 3 and the pressing point of the first pressing part 4, and selecting the walking speed of the first pressing part 4 to determine the time interval between the laser welding point of the first welding torch 3 and the pressing point of the first pressing part 4;

[0071] The pressing force of the second pressing part 4 is selected; the interval between the laser welding point of the second welding gun 3 and the pressing point of the second pressing part 4 is adjusted, and the walking speed of the second pressing part 4 is selected to determine the time interval between the laser welding point of the second welding gun 3 and the pressing point of the second pressing part 4;

[0072] Pressing operation: the first pressing part 4 and the second pressing part 4 are started; the first pressing part 4 follows the first welding gun 3 according to the parameters in the parameter setting and presses the position just welded; the second pressing part 4 follows the second welding gun 3 according to the parameters in the parameter setting and presses the position just welded.

[0073] The first pressing part 4 and the second pressing part 4 in the embodiment are both rollers, which roll the position just welded to strengthen the fusion of the position just welded, wherein the rollers of the first pressing part 4 and the second pressing part 4 are arranged at intervals from the welding guns 3 corresponding thereto, so that the pressing points of the rollers are arranged at intervals from the laser welding points of the welding guns 3 corresponding thereto, and the pressing points of the rollers are behind the laser welding points of the welding guns 3 corresponding thereto. For the case that electrolyte is left between the first skirt 1 and the second skirt 2, the product left between the first skirt 1 and the second skirt 2 after the electrolyte is heated at high temperature can be squeezed out through rolling, so that effective fusion can be achieved. The welding process of the metal shell in the embodiment is mainly used for the case after the electrolyte is injected into the battery cell, and the electrolyte is generally difficult to wipe off from the skirt in the prior art, so that the welding cannot be directly performed.

[0074] In the embodiment, the interval between the laser welding point of the first welding gun 3 and the pressing point of the first pressing part 4 is 0-50 mm, and the interval between the laser welding point of the second welding gun 3 and the pressing point of the second pressing part 4 is 0-50 mm.

[0075] In the embodiment, the welding speed of the first welding gun 3 in the first welding group is the same as the walking speed of the first pressing part 4 of the pressing device, and the welding speed of the second welding gun 3 in the second welding group is the same as the walking speed of the second pressing part 4 of the pressing device.

[0076] In other embodiments, the welding speed of the first welding gun 3 and the walking speed of the first pressing part 4 are not the same. The speeds of the two may be the same for a period of time and different for another period of time.

[0077] The differences between the welding process of the application and the prior art can be obviously embodied in FIGS. 3-7, which are as follows:

[0078] The prior art in FIG. 3 adopts single-sided laser welding, and the process parameters are that a laser welding gun is used to weld the overlapped first metal shell and second metal shell at a power of 600 W and a welding speed of 12 m / s, and the laser welding gun only performs laser heat conduction welding on the outer surface of the first metal shell along a predetermined path. In the figure, the A surface refers to the outer surface of the first metal shell after welding, and the B surface refers to the outer surface of the second metal shell after welding. After welding, it can be clearly seen from FIG. 3 that a heat conduction molten pool is formed at the position of arrow a of the A surface, and then the second metal shell is melted by heat conduction, so that a wavy fusion is formed at the position of arrow d; a metal evaporation hole appears at the position of arrow b due to overheating of the metal, but a welding gap appears at the position of arrow d, and heat cannot be effectively conducted to the second metal layer; overheating and burning of the first metal shell even occur at the position of arrow c, so that the first metal shell is burned through, and the laser directly and uniformly melts the second metal shell.

[0079] Referring to the dashed line h in FIG. 3, FIG. 4 is a metallographic diagram after cutting at the position of the dashed line h, and it can be clearly seen that the first metal shell is broken, and the length of the breakage in the figure is 1.31 mm.

[0080] In comparison with the prior art, referring to FIG. 5, the first welding gun and the second welding gun are used to simultaneously weld from the outer surface of the first metal shell and the outer surface of the second metal shell respectively, and the welding parameters of the first welding gun and the second welding gun are the same, that is, a power of 220 W-380 W, preferably 220 W, 225 W, 250 W, 275 W, 300 W, 350 W, 375 W or 380 W, and a welding speed of 12 m / s. Similarly, the A surface in FIG. 5 refers to the outer surface of the first metal shell after welding, and the B surface refers to the outer surface of the second metal shell after welding, and it can be clearly seen that after the laser welding process of the present application, neither the A surface nor the B surface appears overheating and burning. After comparing FIG. 3 and FIG. 5, it can be seen that the welding effect of the present application is better.

[0081] Referring to FIG. 6, FIG. 6 is a metallographic diagram after cutting along the dashed line position in FIG. 5, and it can be seen that neither the first metal shell nor the second metal shell is burned through when the welding is performed at a power of 300 W and a welding speed of 12 m / s; the effective fusion width of the first metal shell and the second metal shell is 1.85 mm according to the measurement of the metallographic diagram.

[0082] Referring to FIG. 7, the present embodiment also performs a control experiment, and the control experiment is as follows. First, the first metal shell is taken out alone, the first welding gun is used to perform laser heat conduction welding on one side surface of the first metal shell at a power of 300 W and a welding speed of 12 m / s, and the first metal shell subjected to the laser heat conduction welding is photographed, and it can be seen that no overheating and burning phenomenon occurs.

[0083] In other words, Fig. 7 is obtained by applying a power of 300 W to the first metal shell alone by the first welding torch at a welding speed of 12 m / s, or by applying a power of 300 W to the second metal shell alone by the second welding torch at a welding speed of 12 m / s.

[0084] Second embodiment

[0085] The heterolateral double-beam welding process of the second embodiment of the present application differs from the first embodiment in that the interval between the laser welding point of the first welding torch and the pressing point of the first pressing part satisfies the following relationship:

[0086] When the pressing device travels from the pressing point of the first pressing part to the laser welding point of the first welding torch, the temperature of the laser welding point of the first welding torch is more than half of the melting point of the first metal piece;

[0087] Alternatively, the interval between the laser welding point of the second welding torch and the pressing point of the second pressing part satisfies the following relationship:

[0088] When the pressing device travels from the pressing point of the second pressing part to the laser welding point of the second welding torch, the temperature of the laser welding point of the second welding torch is more than half of the melting point of the second metal piece.

[0089] In the present embodiment, the interval between the laser welding point and the pressing point is affected by the moving speed of the welding torch and the moving speed of the pressing device. In the present embodiment, the interval between the laser welding point and the pressing point is generally pre-set, and then one of the following is adopted: the welding torch and the pressing device move at the same speed, and the workpiece is stationary; or the welding torch and the pressing device are both stationary, and the workpiece moves; the speed of the welding torch and the pressing device relative to the workpiece affects the time interval between the welding point and the pressing point, i.e., the temperature of the welding point after the pressing point travels to the laser welding point.

[0090] Third embodiment

[0091] The heterolateral double-beam welding process of the third embodiment of the present application differs from the first embodiment in the lap step and the welding step. In the lap step, the inner surface of the first metal piece is lapped on the inner surface of the second metal piece, and in the present embodiment, the first metal piece is a first sub-skirt, and the second metal piece is a second sub-skirt. In the welding step, laser heat conduction welding is performed simultaneously from the outer surface of the first metal piece and the outer surface of the second metal piece along the same preset welding path by using a laser heat conduction welding device.

[0092] The above merely provides the preferred embodiments of the present application, but should not be used to limit the present application, and any modification, equivalent replacement, and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A contra-directional dual-beam welding process characterized by, The method comprises: a lap step of lapping the inner surface of the first metal piece on the inner surface of the second metal piece; a welding step of simultaneously performing laser heat conduction welding from the outer surface of the first metal piece and the outer surface of the second metal piece along the same preset welding path by using a laser heat conduction welding device; The opposite double-beam welding process should be used in the processing of a battery, which comprises a cover plate, a first metal shell and a second metal shell; the first metal piece in the opposite double-beam welding process is the first metal shell or the cover plate, and the second metal piece is the second metal shell.

2. The off-side dual beam welding process of claim 1, wherein, The method further comprises a pressing step of pressing the welds on the outer surface of the first metal piece and the outer surface of the second metal piece by a pressing device moving along the welding track of the laser heat conduction welding device.

3. The off-side dual beam welding process of claim 1, wherein, The method further comprises a flattening step arranged before the welding step and after the lap step, which comprises: flattening the lapped first metal piece and second metal piece by using a tool.

4. The off-side dual beam welding process of claim 2, wherein, The welding step comprises using a laser heat conduction welding device with a first welding gun (3) and a second welding gun (3); or using two sets of laser heat conduction welding devices, each of which has one welding gun (3), wherein the welding gun (3) of one set of laser heat conduction welding devices is the first welding gun (3), and the welding gun (3) of the other set of laser heat conduction welding devices is the second welding gun (3).

5. The off-side dual beam welding process of claim 4, wherein, The pressing device comprises a first pressing part (4) and a second pressing part (4), the first pressing part (4) and the first welding gun (3) form a first welding group, the first pressing part (4) and the first welding gun (3) are arranged at intervals, so that the laser welding point of the first welding gun (3) and the pressing point of the first pressing part (4) are arranged at intervals; the second pressing part (4) and the second welding gun (3) form a second welding group, the second pressing part (4) and the second welding gun (3) are arranged at intervals and so that the laser welding point of the second welding gun (3) and the pressing point of the second pressing part (4) are arranged at intervals.

6. The off-side dual beam welding process of claim 5, wherein, The interval between the laser welding point of the first welding gun (3) and the pressing point of the first pressing part (4) is 0-50mm, and the interval between the laser welding point of the second welding gun (3) and the pressing point of the second pressing part (4) is 0-50mm; Or, The interval between the laser welding point of the first welding gun (3) and the pressing point of the first pressing part (4) satisfies the following relationship: When the pressing device travels from the pressing point of the first pressing part (4) to the laser welding point of the first welding gun (3), the temperature of the laser welding point of the first welding gun (3) is more than half of the melting point of the first metal piece; Or, the interval between the laser welding point of the second welding gun (3) and the pressing point of the second pressing part (4) satisfies the following relationship: When the pressing device travels from the pressing point of the second pressing part (4) to the laser welding point of the second welding gun (3), the temperature of the laser welding point of the second welding gun (3) is more than half of the melting point of the second metal piece.

7. The off-side dual beam welding process of claim 5, wherein, The welding speed of the first welding gun (3) in the first welding group is the same as the walking speed of the first pressing part (4) of the pressing device; the welding speed of the second welding gun (3) in the second welding group is the same as the walking speed of the second pressing part (4) of the pressing device.

8. The off-side dual beam welding process of claim 1, wherein, The first metal shell has a first skirt (1), and the second metal shell has a second skirt (2); the first skirt (1) comprises a first sub-skirt (11) and a second sub-skirt (12) connected with the first sub-skirt (11), and the second skirt (2) comprises a third sub-skirt (21) and a fourth sub-skirt (22) connected with the third sub-skirt (21); a cover plate is arranged between the second sub-skirt (12) and the fourth sub-skirt (22); the first sub-skirt (11) constitutes a first metal piece, and the third sub-skirt (21) constitutes a second metal piece; the first sub-skirt (11) and the third sub-skirt (21) are both flat plates; The overlapping step comprises overlapping the first sub-skirt (11) on the third sub-skirt (21), and overlapping the second sub-skirt (12) and the fourth sub-skirt (22) on opposite sides of the cover plate (6).

9. The hetero-di-beam welding process of any one of claims 8, wherein, The welding step comprises welding of the first sub-skirt (11) and the third sub-skirt (21), welding of the second sub-skirt (12) and the cover plate (6), and welding of the fourth sub-skirt (22) and the cover plate (6).

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