Method and system for measuring laser welding penetration

Abstract

The invention provides a method and a system for measuring the penetration of laser welding, relates to the technical field of laser welding, and is used for reducing the possibility that a large random error exists between a measured value and an actual value of the penetration. The laser welding fusion depth measuring method comprises the steps that two to-be-welded parts are welded in the welding direction, and a welding seam is formed; cutting the weld joint in the welding direction to obtain a section cutting plane; an included angle alpha is formed between the section cutting plane and the fusion depth direction of the welding seam, and alpha is larger than or equal to-10 degrees and smaller than or equal to 10 degrees; and obtaining the penetration depth of the weld joint on the section cutting plane.

Description

Technical Field

[0001] The present application relates to the technical field of laser welding, and in particular to a method and system for measuring the penetration depth of laser welding. Background Art

[0002] Laser welding is an efficient and precise welding method that uses a high-energy-density laser beam as a heat source. In laser welding technology, one of the important bases for judging welding quality is the penetration depth of the weld.

[0003] In actual situations, due to many influencing factors such as different laser welding power and welding speed, differences in material properties and liquid metal flow, laser spot characteristics, protective gas and environment, etc., the penetration depth of laser welding varies greatly.

[0004] At present, the common method of measuring penetration depth may cause a large random error between the measured penetration depth and the actual value, affecting the judgment of welding quality. Summary of the invention

[0005] The present application provides a method and system for measuring the penetration depth of laser welding, which are used to reduce the possibility of a large random error between the measured penetration depth and the actual value.

[0006] In a first aspect, the present application provides a method for measuring laser welding penetration, comprising:

[0007] Weld the two parts to be welded along the welding direction to form a weld;

[0008] The weld is cut along the welding direction to obtain a section plane; an angle α is formed between the section plane and the penetration direction of the weld, and -10°≤α≤10°;

[0009] Get the penetration of the weld on the cut surface.

[0010] When the above technical solution is adopted, the weld is cut along the welding direction to obtain the cross-section, and there is an angle α between the cross-section and the direction of the weld penetration, -10°≤α≤10°. Therefore, the cross-section can pass through the starting point and the ending point of the weld along the welding direction, and the cross-section can display a metallographic diagram from the starting point to the ending point of the weld. Based on this, when obtaining the penetration of the weld on the cross-section, the penetration of the weld at multiple positions on the cross-section can be obtained. Of course, the penetration curve from the starting point to the ending point of the weld can also be obtained, so as to monitor a larger amount of penetration sample. In specific implementation, the distribution law of the penetration can be obtained based on a larger amount of penetration sample, reducing the possibility of a large random error between the measured penetration value and the actual value. At the same time, the penetration of the weld can be judged more intuitively and effectively, which facilitates the optimization of the laser welding process based on reliable and accurate penetration results.

[0011] In a possible implementation, α=0°.

[0012] When the above technical solution is adopted, the section plane is not only parallel to the welding direction, but also parallel to the penetration direction of the weld. The distance from the weld surface on the section plane along the penetration direction to the bottom of the weld is the penetration, so the penetration of the weld obtained on the section plane is more consistent with the actual situation.

[0013] In a possible implementation, cutting the weld along the welding direction to obtain the section plane includes:

[0014] The weld is cut along the welding direction and along the mid-vertical plane of the weld to obtain the section plane.

[0015] When the above technical solution is adopted, not only the penetration distribution can be fully obtained, but also the high and low points of the periodic changes of the penetration distribution contour lines can be obtained, effectively reducing the possibility of inaccurate test results caused by incomplete test results.

[0016] In a possible implementation, obtaining the penetration depth of the weld on the section plane includes:

[0017] Obtain the penetration depth of the weld in a preset area on the section surface;

[0018] The preset area includes a first boundary and a second boundary along the welding direction, a first preset distance is provided between the first boundary and the starting point of the weld, and a second preset distance is provided between the second boundary and the ending point of the weld.

[0019] When the above technical solution is adopted, the penetration depth of the weld in a preset area on the cross-section surface is obtained, the penetration depth can be obtained more accurately, and the distribution of the penetration depth can be reflected.

[0020] In a possible implementation, obtaining the penetration depth of the weld on the section plane includes:

[0021] Get the minimum and maximum values ​​of the penetration depth;

[0022] Determine the difference in penetration depth based on the maximum and minimum penetration depths;

[0023] The penetration difference is determined as the penetration of the weld on the section plane.

[0024] When the above technical solution is adopted, not only the minimum and maximum values ​​of the weld penetration depth are obtained to determine whether the penetration depth is within the preset range, but also the penetration difference can be used as a basis for reflecting whether the penetration depth is evenly distributed and whether the welding quality is consistent.

[0025] In a possible implementation, welding two parts to be welded along a welding direction to form a weld includes:

[0026] At least one of continuous laser welding, annular laser welding or red and blue laser welding is used to weld two parts to form a weld.

[0027] In a possible implementation, cutting the weld along the welding direction to obtain the section plane includes:

[0028] The weld is cut along the welding direction by using at least one of grinding wheel cutting, electric spark wire cutting or machining to obtain a section surface.

[0029] In a possible implementation, obtaining the penetration depth of the weld on the section plane includes:

[0030] Obtaining images of the cut surface in electronic format;

[0031] Determine the penetration of the weld on the cut surface based on the electronic format image.

[0032] In a possible implementation, after obtaining the penetration depth of the weld on the cross-section surface, the method for measuring the penetration depth of laser welding further includes determining the quality of the weld according to the penetration depth.

[0033] In a second aspect, the present application provides a system for measuring laser welding penetration, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the method for measuring laser welding penetration of the first aspect are implemented.

[0034] The beneficial effects of the laser welding penetration measurement system provided in the present application can refer to the beneficial effects of the laser welding penetration measurement method provided in the first aspect above, and will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the steps of a method for measuring laser welding penetration provided in an embodiment of the present application.

[0036] Figure 2 This is a schematic diagram of welding using a heat conduction laser welding method provided in an embodiment of the present application.

[0037] Figure 3 for Figure 2 Schematic diagram of the metallographic structure of the mid-vertical plane of the weld formed in .

[0038] Figure 4 for Figure 3 At the first position in Figure 2 Schematic diagram of the metallographic structure formed by cutting in a direction perpendicular to the welding direction.

[0039] Figure 5 for Figure 3 At the second position in Figure 2Schematic diagram of the metallographic structure formed by cutting in a direction perpendicular to the welding direction.

[0040] Figure 6 A schematic diagram of welding using laser deep penetration welding provided in an embodiment of the present application.

[0041] Figure 7 for Figure 6 Schematic diagram of the metallographic structure of the mid-vertical plane of the weld formed in .

[0042] Figure 8 for Figure 7 At the third position in Figure 6 Schematic diagram of the metallographic structure formed by cutting in a direction perpendicular to the welding direction.

[0043] Fig. 9 for Figure 7 At the fourth position in Figure 6 Schematic diagram of the metallographic structure formed by cutting in a direction perpendicular to the welding direction.

[0044] Fig.10 A schematic top view of the first cross-section of the weld formed by welding the top cover of the square aluminum shell battery cell provided in an embodiment of the present application to the positive and negative electrode current collectors during metallographic cutting.

[0045] Fig.11 It is a schematic diagram of the second cross-section of the weld formed after the top cover and the shell of the cylindrical battery cell are welded.

[0046] Description of reference numerals:

[0047] 11-first laser, 12-first workpiece to be welded, 13-first molten pool, 14-first weld, 141-first position,

[0048] 142 - second position;

[0049] 21-second laser, 22-second workpiece to be welded, 23-second molten pool, 24-second weld, 241-third position,

[0050] 242-4th position, 25-keyhole;

[0051] 31-positive and negative electrode current collectors, 32-top cover component, 33-third weld seam, 34-first section plane;

[0052] 41 - shell, 42 - top cover, 43 - fourth weld, 44 - second section plane. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification, claims and drawings of this application are intended to cover non-exclusive inclusions.

[0055] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase "embodiments" in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0056] The directional words appearing in the following description are all directions shown in the figures, and do not limit the specific structure of the current limiting module of the present application. For example, in the description of the present application, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0057] In addition, the terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0058] In the description of the present application, unless otherwise specified, "plurality" means more than two (including two), and similarly, "multiple groups" means more than two groups (including two).

[0059] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, the "connection" or "connection" of a mechanical structure may refer to a physical connection. For example, the physical connection may be a fixed connection, such as a fixed connection through a barrier, such as a fixed connection through screws, bolts or other barrier; the physical connection may also be a detachable connection, such as a mutual snap-on or snap-fit ​​connection; the physical connection may also be an integral connection, such as a connection formed by welding, bonding or integral molding. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0060] Laser welding is widely used due to its high efficiency, precision, non-contact welding, and strong material adaptability.

[0061] Laser welding can be divided into two types: heat conduction laser welding and laser deep penetration welding.

[0062] Among them, heat conduction laser welding generally uses laser radiation to heat the surface of the area to be welded on the workpiece to be welded. The surface heat diffuses to the inside through heat conduction. By controlling laser parameters such as the width, energy, peak power and repetition frequency of the laser pulse, the area to be welded on the workpiece to be welded is melted to form a specific molten pool.

[0063] Laser deep penetration welding generally uses a continuous laser beam to complete the welding of the parts to be welded. Its metallurgical physical process is very similar to electron beam welding, that is, the energy conversion mechanism is completed through the "key-hole" structure. Under sufficiently high power density laser irradiation, the material evaporates and forms a keyhole. The keyhole can completely absorb the injected laser energy and melt the metal surrounding the cavity. The flow of the liquid outside the hole wall and the surface tension of the wall layer are in a dynamic balance with the steam pressure continuously generated in the cavity. The laser beam carries a large amount of light energy and continuously enters the keyhole, and the material outside the keyhole is flowing continuously. As the laser beam moves forward along the welding direction, the keyhole is always in a stable state of flow. After the keyhole moves forward along the welding direction with the laser beam, the molten metal fills the cavity left after the keyhole is removed and then condenses into a weld, completing the welding process.

[0064] In the field of battery cells, laser welding is widely used due to its fast welding speed, high adaptability to materials, and high weld strength. It is used to achieve sealing welding of battery cell components or welding of connecting devices, thereby achieving the purpose of sealing or current passing of battery cell components.

[0065] In actual situations, due to many influencing factors such as different laser welding power and welding speed, differences in material properties and liquid metal flow, laser spot characteristics and environment, the depth of the molten pool (i.e., the penetration depth) of the weld formed by laser welding ultimately varies greatly.

[0066] When the penetration depth is too small, it may lead to unreliable connection or insufficient overcurrent, resulting in poor sealing or temperature rise caused by heat accumulation, and in severe cases, thermal runaway. When the penetration depth is too large, it may cause the welding carrier to be welded through. For example, laser leakage in the top cover welding may cause the diaphragm or pole piece to be burned, which may cause self-discharge problems of the battery cell.

[0067] In the prior art, in order to solve the problem of large differences in welding depth, it is necessary to control various welding parameters, such as adjusting the defocusing amount, welding pulse width, frequency, peak value, energy and power, or taking measures such as blowing nitrogen shielding gas, etc. However, large differences in welding depth still occur during the welding process.

[0068] In addition, due to the different laser powers used during welding, in general, when using lower power for heat conduction laser welding, only the surface of the welded area of ​​the welded parts melts, and the resulting molten pool is shallow. When using higher power for deep penetration laser welding, the resulting molten pool is deeper. When the laser power is near the critical condition for keyhole formation, laser deep penetration welding and heat conduction laser welding may be performed alternately, which will also lead to a large difference in the depth of weld penetration.

[0069] In the field of laser welding technology, the penetration depth of the weld is one of the important parameters for determining the stability and quality reliability of welding.

[0070] It is usually necessary to effectively evaluate the penetration depth of the weld by cutting metallography in order to further optimize the welding quality.

[0071] The common method of measuring penetration depth at present may result in a large random error between the measured penetration depth and the actual value, which in turn affects the judgment of the laser welding quality.

[0072] In order to solve the technical problems existing in the above-mentioned prior art, see Figure 1 As shown, an embodiment of the present application provides a method for measuring the laser welding penetration depth. It should be noted that the executor of the method for measuring the laser welding penetration depth provided in the embodiment of the present application is a device for measuring the laser welding penetration depth.

[0073] The method for measuring laser welding penetration provided in the embodiment of the present application comprises the following steps:

[0074] Step S1: Weld two parts to be welded along a welding direction to form a weld.

[0075] In specific implementation, the welding direction can be determined based on factors such as the specific shape, material, thickness and welding process requirements of the two parts to be welded, so as to ensure the quality of the weld, improve welding efficiency, and reduce problems such as welding deformation and stress concentration.

[0076] The two parts to be welded are welded along the welding direction, and the formed weld can be a straight weld, of course, it can also be a curved weld.

[0077] It can be understood that, when two parts to be welded are welded along the welding direction, the extension direction of the formed weld is consistent with the welding direction.

[0078] Step S2: cutting the weld along the welding direction to obtain a section plane. An angle α is formed between the section plane and the penetration direction of the weld, where -10°≤α≤10°.

[0079] In specific implementation, the weld can be cut by at least one of grinding wheel cutting, electric spark wire cutting or machining to obtain a section surface.

[0080] Specifically, the weld can be cut along the welding direction by using any one of grinding wheel cutting, electric spark wire cutting or machining.

[0081] Of course, a combination of two of the methods may also be used, for example, a combination of grinding wheel cutting and electric spark wire cutting, or a combination of grinding wheel cutting and machining, to cut the weld along the welding direction.

[0082] Furthermore, the weld can be cut along the welding direction by combining grinding wheel cutting, wire EDM and machining.

[0083] The specific method used to cut the weld and obtain the cross-section surface is not specifically limited here and is subject to actual conditions.

[0084] It should be noted that the direction of the weld penetration is the direction from the surface of the weld to the bottom of the weld. The direction of the weld penetration of the weld in the welding area is consistent for different welds.

[0085] There is an angle α between the section plane and the penetration direction of the weld, and -10°≤α≤10°.

[0086] It can be understood that when the weld is a straight weld, the cross-section formed by cutting the weld along the welding direction is a plane, and when the weld is a curved weld, the cross-section formed by cutting the weld along the welding direction is a curved surface.

[0087] Illustratively, the angle α between the section plane and the penetration direction of the weld can be -10°, -8°, -6°, -2°, 1°, 3°, 5°, 8°, or 10°, which is not specifically limited here.

[0088] Step S3: Obtain the penetration depth of the weld on the section surface.

[0089] After the weld is cut to form a cross-section, a metallographic diagram of the weld is shown on the cross-section, through which the penetration depth of the weld on the cross-section can be obtained.

[0090] When the penetration depth is obtained by using the laser welding penetration measurement method provided in the embodiment of the present application, the weld is cut along the welding direction to obtain the section plane, and there is an angle α between the section plane and the penetration direction of the weld, -10°≤α≤10°. Therefore, the section plane can pass through the starting point and the end point of the weld along the welding direction, and the metallographic schematic diagram from the starting point to the end point of the weld can be displayed on the section plane. Based on this, when obtaining the penetration depth of the weld on the section plane, the penetration depth of the weld at multiple positions on the section plane can be obtained. Of course, the penetration depth curve from the starting point to the end point of the weld can also be obtained, so as to monitor a larger amount of penetration depth samples. In specific implementation, the distribution law of the penetration depth can be obtained based on a larger amount of penetration depth samples, reducing the possibility of a large random error between the measured penetration depth and the actual value. At the same time, the penetration depth of the weld can be judged more intuitively and effectively, so as to facilitate the optimization of the laser welding process based on reliable and accurate penetration depth results.

[0091] As an alternative, α=0°.

[0092] When α=0°, the section plane is not only parallel to the welding direction, but also parallel to the direction of the weld penetration. In this way, the distance between the weld surface on the section plane and the weld bottom at the corresponding position can be directly measured, and this distance is the penetration. In this case, the penetration of the weld obtained on the section plane is more consistent with the actual situation.

[0093] In a possible implementation, the specific implementation of cutting the weld along the welding direction and obtaining the section surface in step S2 may be:

[0094] The weld is cut along the welding direction and along the mid-vertical plane of the weld to obtain the section plane.

[0095] It should be noted that by studying the temperature field distribution during welding for different welding processes and comparing the penetration distribution formed under different temperature field distributions, the contour spectrum of penetration distribution is obtained. Generally speaking, during actual welding, the higher the temperature at the welding position, the stronger the energy field and the greater the penetration.

[0096] The penetration distribution contour spectrum of the weld usually has a high degree of overlap with the isothermal spectrum formed by the temperature of the welding position along the weld during the welding process. The penetration distribution contour lines usually show continuous periodic changes, and the isothermal spectrum formed by the temperature of the welding position along the weld during the welding process usually almost overlaps with the mid-vertical plane of the weld along the welding direction.

[0097] When obtaining the section plane, the present application cuts the weld along the welding direction and along the mid-vertical plane of the weld to obtain the section plane. In this way, not only can the penetration distribution be fully obtained, but also the high and low points of the periodic changes of the penetration distribution contour line can be obtained, effectively reducing the possibility of inaccurate test results caused by incomplete test results.

[0098] It can be seen from this that the laser welding penetration measurement method provided in the present application cuts the weld along the welding direction and along the mid-vertical plane of the weld, that is, cutting along the line direction covering the highest and lowest penetration points to obtain a cross-sectional surface to fully reflect the welding effect, facilitate accurate and efficient identification of problems with poor welding penetration, and provide direction for optimization of the welding process.

[0099] Specifically, Figure 2 The schematic diagram of welding using heat conduction laser welding is shown. The first laser 11 moves along the first welding direction relative to the first workpiece 12 to be welded, and the first workpiece 12 to be welded only undergoes surface melting to generate a shallow first molten pool 13, and a first weld 14 is formed after welding.

[0100] The first weld 14 is cut along the first welding direction and along the mid-vertical plane of the first weld 14 to obtain a section plane, as shown in FIG. Figure 3 The metallographic diagram is shown.

[0101] Figure 4 Indicate Figure 3 A schematic metallographic diagram is shown in FIG. 1 , formed by cutting at the first position 141 in a direction perpendicular to the first welding direction. Figure 5 Indicate Figure 3 A schematic metallographic diagram is shown in FIG. 1 , formed by cutting at the second position 142 in a direction perpendicular to the first welding direction.

[0102] Combination Figures 3 to 5 It can be seen that the penetration depths at different positions on the first weld 14 are different, and the penetration depth at the second position 142 is greater than the penetration depth at the first position 141 .

[0103] In the prior art, generally, the penetration depth at a specific position is obtained along a direction perpendicular to the first welding direction, such as only obtaining the penetration depth at the first position or the second position, which is random and has a large error. However, the present application cuts the first weld 14 along the first welding direction and along the mid-vertical plane of the first weld 14 to obtain a section surface, such as Figure 3 In this way, a larger number of penetration samples can be obtained, the actual penetration of the welding can be effectively identified, and the laser welding process can be optimized based on reliable and accurate penetration results.

[0104] Furthermore, if Figure 6 The schematic diagram of laser deep penetration welding is shown. The second laser 21 moves along the second welding direction relative to the second workpiece 22 to be welded, and the molten metal fills the keyhole 25 to generate a deeper second molten pool 23, and a second weld 24 is formed after welding.

[0105] The second weld 24 is cut along the second welding direction and along the mid-vertical plane of the second weld 24 to obtain a section plane, as shown in FIG. Figure 7 The metallographic diagram is shown.

[0106] Figure 8 Indicate Figure 7 A schematic metallographic diagram of the third position 241 in FIG. 1 , cut along a direction perpendicular to the second welding direction. Fig. 9 Indicate Figure 7 A schematic metallographic diagram of the fourth position 242 in FIG. 1 , cut along a direction perpendicular to the second welding direction.

[0107] Combination Figures 7 to 9 It can be seen that the penetration depths at different positions on the second weld 24 are not the same, and the penetration depths of the second weld 24 vary greatly.

[0108] like Figure 8 and Fig. 9 As shown in the figure, the measured penetration depths at different cutting positions are significantly different.

[0109] In the prior art, generally only the penetration depth at a specific position is obtained along the direction perpendicular to the second welding direction, such as only the penetration depth at the third position or the fourth position, which is random and has a great difference from the actual penetration depth. However, the present application adopts the method of cutting the second weld 24 along the second welding direction and along the mid-vertical plane of the second weld 24 to obtain the section surface, such as Figure 7 As shown. In this way, when the depth of the molten pool varies greatly, a suitable metallographic penetration measurement method is selected to monitor more samples, effectively identify the true penetration of the welding, and then optimize the laser welding process based on reliable and accurate penetration results.

[0110] In some embodiments, the specific implementation method of obtaining the penetration depth of the weld on the section surface in step S3 may be:

[0111] Get the penetration of the weld at a preset area on the section surface.

[0112] The preset area includes a first boundary and a second boundary along the welding direction, a first preset distance is between the first boundary and the starting point of the weld, and a second preset distance is between the second boundary and the ending point of the weld.

[0113] like Figure 3 and Figure 7 As shown in the figure, at the beginning of welding, the power is small, the temperature is low, and the penetration is shallow. After a certain welding time and a certain length of weld, the parameters such as power and temperature tend to be stable, and the penetration of the weld is relatively deep. When welding is terminated, the penetration is shallow.

[0114] In a specific implementation, the penetration depth of the weld in a preset area on the cross-section surface is obtained, which can more accurately obtain the penetration depth and reflect the actual situation of the penetration depth distribution.

[0115] The specific values ​​of the first preset distance and the second preset distance are not specifically limited here, and are subject to actual conditions. For example, the ratio of the first preset distance and the second preset distance to the weld length can be limited. For example, the ratio of the first preset distance and the second preset distance to the weld length can be 1:10, 1:9, etc.

[0116] Regarding the specific implementation method of obtaining the penetration depth of the weld on the cross-section surface in step S3, the present application provides at least the following two methods.

[0117] First way:

[0118] Step S31: obtaining the minimum value and the maximum value of the penetration depth;

[0119] Step S32: determining a penetration depth difference according to the maximum penetration depth and the minimum penetration depth;

[0120] Step S33: Determine the penetration depth difference as the penetration depth of the weld on the section surface.

[0121] Specifically, after cutting the weld along the welding direction and obtaining the cross-section, the penetration depths of the weld at multiple positions within a preset area on the cross-section can be obtained, and the multiple penetration depths can be compared to obtain the maximum and minimum penetration depths. The maximum and minimum penetration depths are subtracted to obtain the penetration difference.

[0122] When the above technical solution is adopted, not only the minimum and maximum values ​​of the weld penetration depth are obtained to determine whether the penetration depth is within the preset range, but also the penetration difference can be used as a basis for reflecting whether the penetration depth is evenly distributed and whether the welding quality is consistent.

[0123] In actual situations, the minimum penetration depth is approximately equal to 0-90% of the maximum penetration depth. For example, the minimum penetration depth is approximately equal to 10%, 30%, 50%, 60%, 80%, 90%, etc. of the maximum penetration depth, but of course, it is not limited thereto.

[0124] In specific implementation, the minimum and maximum values ​​of the penetration depth in the preset area can be obtained. Then, the penetration difference is determined based on the maximum and minimum values ​​of the penetration depth in the preset area. After that, the penetration difference is determined as the penetration depth of the weld on the section surface. In this way, the penetration depth can be obtained more accurately and the penetration depth distribution can be reflected.

[0125] Second way:

[0126] Step S301: obtaining an electronic format image of the section surface;

[0127] Step S302: Determine the penetration depth of the weld on the section surface according to the electronic format image.

[0128] In specific implementation, the sample of the cross section can be placed on the stage of a metallographic microscope, the cross section of the test can be observed through the objective lens, and the sample on the stage can be photographed using imaging software to obtain an electronic format image of the cross section.

[0129] Load the electronic format image into the metallographic software in the computer and measure the distance from the weld surface to the bottom of the weld at the corresponding position, which is the penetration depth.

[0130] In a possible implementation, welding two parts to be welded along a welding direction to form a weld includes:

[0131] At least one of continuous laser welding, annular laser welding or red and blue laser welding is used to weld two parts to form a weld.

[0132] Specifically, any one of continuous laser welding, circular laser welding or red and blue laser welding can be used to weld two parts to form a weld.

[0133] Of course, a combination of two of the methods may also be used, for example, a combination of continuous laser welding and circular laser welding, or a combination of circular laser welding and red and blue laser welding, to weld two parts to be welded to form a weld.

[0134] Furthermore, the two parts to be welded can be welded to form a weld by using a continuous laser welding method, a circular laser welding method or a combination of red and blue laser welding methods.

[0135] The specific welding method used to weld the two parts to be welded to form a weld is not specifically limited here and is subject to actual conditions.

[0136] In a possible implementation, after obtaining the penetration depth of the weld on the section surface, the method for measuring the penetration depth of laser welding further includes:

[0137] Step S4: Determine the quality of the weld according to the penetration depth.

[0138] Generally, the weld penetration is required to be within the preset range and be relatively uniform. At this time, the weld quality is better and the weld quality consistency is better.

[0139] In actual situations, a first threshold and a second threshold can be set in a laser welding penetration measurement device. After cutting the weld along the welding direction and obtaining the cross-section, the penetration of the weld at multiple positions within a preset area on the cross-section can be obtained.

[0140] For the convenience of description, the penetration depths of the weld at multiple positions within a preset area on the cross-sectional plane are defined as multiple penetration depths.

[0141] First, the multiple penetration depths can be compared with a first threshold value, and when the multiple penetration depths are all within the first threshold range, it can be determined that the quality of the weld is good. Alternatively, according to a certain ratio, for example, when 80% of the multiple penetration depths are within the first threshold range, it is determined that the quality of the weld is good.

[0142] In addition, the maximum and minimum penetration depths of the multiple penetration depths can be compared and subtracted to obtain a penetration difference, which is then compared with a second threshold. When the penetration difference is within the range of the second threshold, it can be concluded that the penetration is more uniform and the quality of the weld is better.

[0143] In addition to the above, the present application also provides a laser welding penetration measurement system, including a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, the steps of the above-mentioned laser welding penetration measurement method are implemented.

[0144] In specific implementations, the memory can be used to store software programs and modules, such as the program instructions / modules corresponding to the laser welding penetration measurement method in the embodiment of the present application. The processor executes various functional applications and data processing by running the software programs and modules stored in the memory, thereby realizing the above-mentioned laser welding penetration measurement method.

[0145] The memory may include a high-speed random access memory, and may also include a non-volatile memory (non-volatile memory) or a volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. For example, flash memory, hard disk, multimedia card, card-type memory (for example, SD or DX memory, etc.), random access memory (random access memory, RAM), read-only memory (read-only memory, ROM), erasable programmable read-only memory (erasable programmable read-only memory, EPROM), electrically erasable programmable read-only memory (electrically erasable programmable read-only memory, EEPROM), programmable read-only memory (programmable read-only memory, PROM), magnetic memory, magnetic disk, optical disk, etc., and RAM may include static RAM or dynamic RAM.

[0146] The processor may be a central processing unit (CPU), a controller, a microcontroller, a microprocessor, or other data processing chip. The processor may also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. A general-purpose processor may be a microprocessor or the processor may also be any conventional processor, such as a single-chip microcomputer.

[0147] The beneficial effects of the laser welding penetration measurement system provided in the present application can refer to the beneficial effects of the above-mentioned laser welding penetration measurement method, which will not be described in detail here.

[0148] Below, the laser welding penetration measurement method and system provided in the embodiments of the present application are applied to the field of battery cells as an example for explanation. Of course, this is just an example and is not a specific limitation.

[0149] In the welding process of each component of the battery cell, it is necessary to consider not only the internal resistance of each component itself, but also the welding composite effect of the welding connection area. Otherwise, the connection reliability is poor, resulting in welding defects such as poor quality reliability of the battery cell or lack of sealing. What's more, it will cause the internal resistance of the battery to be too large, and even affect the safety of the entire battery system.

[0150] In one example, if Fig.10 As shown, for the square aluminum shell battery cell, continuous laser welding is used to weld the connection between the positive and negative electrode collectors 31 (also called pole ears) and the top cover component 32 of the square aluminum shell battery cell to obtain a third weld 33.

[0151] In actual situations, in addition to ensuring the stability of the core in the square aluminum shell battery cell, the connection here also needs to ensure the flow of current between the positive and negative electrode collectors 31 and the outside of the square aluminum shell battery cell.

[0152] Therefore, in addition to detecting the pulling force of the positive and negative electrode current collectors 31 on the top cover component 32 , it is more important to monitor the quality reliability of the connection here according to the penetration depth of the third weld 33 .

[0153] As mentioned above, the depth of penetration contour spectrum is positively correlated with the temperature field contour spectrum, and the temperature field contour spectrum usually almost overlaps with the median vertical plane of the welding direction. Therefore, when cutting the metallographic structure, a more complete and intuitive diagram of the depth of penetration can be obtained by cutting along the median vertical plane of the third weld 33 parallel to the welding direction.

[0154] Specifically, along the Fig.10 The first section plane 34 shown cuts the third weld seam 33 , and the first section plane 34 is a mid-vertical plane along the third weld seam 33 and parallel to the welding direction.

[0155] In another example, Fig.11 As shown, for cylindrical batteries, the red-blue composite laser welding method is selected to weld the shell 41 and the top cover 42 of the battery cell to obtain the fourth weld 43. The connection here is mainly to ensure the sealing of the battery cell. In addition to testing the tensile strength of the sample after welding, it is also necessary to monitor the welding quality according to the depth of penetration of the weld.

[0156] When cutting metallographic structure, by cutting along the mid-vertical plane of welding direction, a more complete and intuitive picture of the penetration depth can be obtained, so as to further optimize the welding process.

[0157] Specifically, along the Fig.11 The second section plane 44 shown cuts the fourth weld 43 , and the second section plane 44 is a perpendicular midplane along the fourth weld 43 and parallel to the welding direction.

[0158] From the above, it can be seen that in order to ensure the consistency of the quality of battery cell components, it is of great significance to select an optimal cutting path to fully reflect the laser welding effect.

Claims

1. A method for measuring laser welding penetration, characterized in that: include: Weld the two parts to be welded along the welding direction to form a weld; The weld is cut along the welding direction to obtain a section plane; an angle α is formed between the section plane and the penetration direction of the weld, wherein -10°≤α≤10°; The penetration depth of the weld on the cutting plane is obtained.

2. The method for measuring laser welding penetration according to claim 1, characterized in that: The α=0°.

3. The method for measuring laser welding penetration according to claim 2, characterized in that: The step of cutting the weld along the welding direction to obtain a section plane comprises: The weld is cut along the welding direction and along the mid-vertical plane of the weld to obtain a section plane.

4. The method for measuring laser welding penetration according to claim 1, characterized in that: The obtaining of the penetration depth of the weld on the section plane comprises: Obtaining the penetration depth of the weld in a preset area on the section surface; The preset area includes a first boundary and a second boundary along the welding direction, a first preset distance exists between the first boundary and a starting point of the weld, and a second preset distance exists between the second boundary and an ending point of the weld.

5. The method for measuring laser welding penetration according to claim 1, characterized in that: The obtaining of the penetration depth of the weld on the section plane comprises: Obtaining a minimum value of the penetration depth and a maximum value of the penetration depth; Determining a penetration depth difference according to the maximum penetration depth and the minimum penetration depth; The penetration difference is determined as the penetration of the weld on the cut plane.

6. The method for measuring laser welding penetration according to any one of claims 1 to 5, characterized in that: The step of welding two parts to be welded along a welding direction to form a weld includes: At least one of continuous laser welding, annular laser welding or red and blue laser welding is used to weld two parts to form a weld.

7. The method for measuring laser welding penetration according to any one of claims 1 to 5, characterized in that: The step of cutting the weld along the welding direction to obtain a section plane comprises: The weld is cut along the welding direction by at least one of grinding wheel cutting, electric spark wire cutting or machining to obtain a section surface.

8. The method for measuring laser welding penetration according to claim 1, characterized in that: The obtaining of the penetration depth of the weld on the section plane comprises: Acquiring an electronic format image of the section; The penetration depth of the weld on the cut surface is determined based on the electronic format image.

9. The method for measuring laser welding penetration according to claim 5, characterized in that: After obtaining the penetration depth of the weld on the section plane, the method for measuring the penetration depth of laser welding further includes: The quality of the weld is determined based on the penetration depth.

10. A laser welding penetration measurement system, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method for measuring laser welding penetration according to any one of claims 1 to 9 are implemented.

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