A method for welding plastics and metals

Abstract

The application provides a welding method for plastic and metal, through first welding, setting specific defocusing amount, frequency and first laser power, generating bubbles and forming effective welding area; through second welding, setting specific defocusing amount, frequency and first laser power, making the weld edge formed after the first welding melt again during the second welding, so that the bubbles are filled with the plastic melted again in the weld area, and the gas in the bubbles can escape from the weld edge melted again, which ensures the welding strength and avoids the influence of the bubbles on the weld, and solves the welding problem between the plastic and the metal.

Description

Technical Field

[0001] The present invention relates to an application of laser, in particular to a welding method for plastic and metal. Background Art

[0002] Laser welding is a highly efficient and precise welding method that utilizes a high-energy-density laser beam as a heat source. It is a key application of laser material processing technology. It is primarily used for welding thin-walled materials and at low speeds. The welding process is heat-conduction-based, meaning that laser radiation heats the workpiece surface, which then diffuses inward through heat conduction. By controlling parameters such as the laser pulse width, energy, peak power, and repetition rate, the workpiece is melted, forming a specific molten pool. Due to its unique advantages, it has been successfully applied to the precision welding of micro and small parts. Laser welding offers high quality, high precision, low deformation, high efficiency, and high speed.

[0003] Many automotive and biomedical products are made from a combination of polymers (or plastics) and lightweight metals (or metal alloys / ceramics), leveraging the strengths of each material. However, due to significant differences in the physical and chemical properties of polymers and metals, achieving reliable welds using conventional welding methods is difficult.

[0004] Laser welding involves rapid heating and cooling, a process that creates uneven weld composition and structure. This leads to the potential for a range of welding defects, such as porosity, cracks, and inclusions. Porosity is the most common defect in laser welding, and even dense materials can be susceptible to this problem.

[0005] Porosity is primarily caused by three factors: (1) high-temperature decomposition of the weld metal; (2) gas trapped in the pores of the transition layer; and (3) the influx of shielding gas. The mechanism of pore formation is as follows: Liquid metal in the molten pool dissolves a significant amount of gas at high temperatures, and the gas trapped in the pores of the transition layer also enters the pool. As the temperature drops, the gas solubility decreases, and the gas precipitates. If the rising velocity of the precipitated gas is slower than the solidification rate of the molten pool, pores will form within the weld.

[0006] The prior art discloses a welding method for plastics and metals for removing weld bubbles. This method sets the bottom of the butt joint of the sample to be welded in the air, pre-sets an AC electromagnetic field below it, and sets the laser welding work head above the sample and the AC electromagnetic field below the sample to remain stationary during the laser welding process. The laser beam is focused on the upper surface of the aluminum alloy, and the magnetic field action range always covers the entire molten pool area until the laser deep penetration welding is completed, thereby ensuring that the weld penetration remains unchanged while minimizing the weld porosity.

[0007] The above-mentioned method in the prior art requires additional use of a special device to eliminate weld bubbles, which makes the structure of the entire laser welding device more complicated, the operation more cumbersome, and the cost more expensive. Summary of the Invention

[0008] In view of this, the present invention provides a method for welding plastic and metal, which is used to solve the technical problem of bubbles in the prior art.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A method for welding plastic and metal, characterized by comprising the following steps:

[0011] S1: clamping workpiece 1 and workpiece 2 to be welded, forming a weld at the contact position between workpiece 1 and workpiece 2; adjusting the defocus amount, frequency and first laser power of the laser emitting device; workpiece 1 is plastic, and workpiece 2 is metal;

[0012] S2 starts the laser emitting device, and the laser beam emitted by the laser emitting device irradiates the weld and moves along the preset weld until a molten pool is formed at the weld, and then stops laser irradiation;

[0013] S3: keeping the workpiece 1 and the workpiece 2 in a clamped state and allowing them to cool;

[0014] S4 adjusts the second laser power of the laser emitting device, starts the laser emitting device again, irradiates the laser beam emitted by the laser emitting device on the weld, and moves the laser beam emitted by the laser emitting device along the moving trajectory of the laser beam in step S2;

[0015] If the bubbles in the weld are completely eliminated in step S5, the laser welding is completed; if there are still bubbles in the weld, repeat steps S3-S4 until the bubbles in the weld are completely eliminated, and the laser welding is completed;

[0016] The second laser power in step S4 is less than the first laser power in step S2, and the second laser power makes the heat generated by the laser beam greater than or equal to the melting point of the workpiece 1, and the second laser power makes the heat generated by the laser beam less than the temperature at which the workpiece 1 decomposes.

[0017] Preferably, the negative defocus amount of the second welding in step S4 is greater than the negative defocus amount of the first welding in step S1, and the negative defocus amount of the first welding is -5mm to -30mm.

[0018] Preferably, in step S1, the first laser power is adjusted so that the welding process can produce a connection with an appropriate amount of bubbles.

[0019] Preferably, in step S2, when a molten pool with a depth of 0.1 mm to 2 mm or a width of 10 mm to 30 mm is formed at the weld, the laser irradiation can be stopped.

[0020] Preferably, in step S3, the ambient temperature during the standing state is room temperature (20°C to 28°C), and the weld is cooled until the weld temperature is lower than the melting point of the workpiece 1, that is, the weld melt has solidified.

[0021] Preferably, the second laser power is 40% to 80% of the first laser power.

[0022] Preferably, in step S2, the moving speed of the laser beam is 1 mm / s to 3 mm / s, and in step S4, the moving speed of the laser beam is 4 mm / s to 7 mm / s.

[0023] Preferably, in step S2, the frequency of the laser beam output by the laser emitting device is 20 Hz to 40 Hz.

[0024] Preferably, in step S4, the frequency of the laser beam output by the laser emitting device is the same as that in step S2.

[0025] Preferably, in step S5, bubble defects are detected by online ultrasonic testing.

[0026] The present application addresses the problem of bubbles during the welding process of polymer materials (or plastics) and lightweight metals (or metal alloys / ceramics). During the first welding, a specific defocus amount, frequency and first laser power are set to generate bubbles and form an effective welding area. During the second welding, a specific defocus amount, frequency and first laser power are set so that the plastic at the edge of the weld formed after the first welding is melted again during the second welding. In this way, while the bubbles are filled with the re-melted plastic in the weld area, the gas inside them can escape from the re-melted weld edge, which not only ensures the welding strength but also avoids the influence of bubbles on the weld, thus effectively solving the welding problem between plastic and metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0028] Figure 1Schematic diagram of the welding method for plastic and metal according to the present invention;

[0029] Figure 2 This is a structural diagram of the first welding seam of the welding method for plastic and metal according to the present invention;

[0030] Figure 3 This is a structural diagram of the second welding seam of the welding method for plastic and metal according to the present invention.

[0031] Figures: 1-workpiece 1; 2-workpiece 2; 3-laser emitting device; 4-fixture. DETAILED DESCRIPTION

[0032] In view of this, the present invention provides a welding method for plastic and metal, which is used to solve the technical problem of bubbles in the prior art.

[0033] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0034] In order to illustrate the present invention in more detail, the welding method for plastic and metal provided by the present invention is specifically described below with reference to the accompanying drawings.

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0036] Example 1:

[0037] See attached Figure 1 The above workpiece 1 is made of PET material, and the workpiece 2 is made of stainless steel;

[0038] Step S1. Clamp the workpiece 1 and the workpiece 2 to be welded together by the fixture 4, so that the workpiece 1 and the workpiece 2 are subjected to uniform clamping force, and a weld is formed at the position where the workpiece 1 and the workpiece 2 meet; adjust the defocus amount and the first laser power of the laser emitting device 3; the fixture 4 used is as follows: Figure 1 As shown, the clamp 4 applies up and down forces to clamp the workpiece 1 and the workpiece 2, and there are no excessive restrictions on the clamp 4.

[0039] In step S1, the method for adjusting the first laser power is to conduct trial welding. The parameters are adjusted so that the welding process can produce a connection with an appropriate amount of bubbles. Experimental research results show that bubbles are formed due to the decomposition of plastic due to heat. If the heat input is too small, although the formation of bubble defects can be avoided, the energy input is too low and a weld cannot be formed or the strength of the joint between the two does not meet the requirements. The generation of bubbles can squeeze the molten plastic toward the side of the second workpiece, allowing the plastic melt to enter the microstructure of the second workpiece surface to form an anchoring effect. Therefore, the generation of bubbles is conducive to the formation of the weld. However, once the weld is formed and cooled, the bubbles will be trapped in the weld, weakening the strength of the weld. Therefore, the formation of an appropriate amount of bubbles in the weld should be encouraged during the welding process, and the bubble defects should be eliminated after the weld is formed. Based on the stainless steel material of the second workpiece, the general welding temperature is 1400℃.

[0040] Step S2. Start the laser emitting device 3. The laser beam emitted by the laser emitting device 3 is irradiated on the weld and moves along the preset weld until a molten pool is formed at the weld, and then the laser irradiation is stopped; the above-mentioned first laser power is 60W, and the defocus amount is adjusted to -5mm~-30mm. The moving speed of the laser beam in step S2 is 3mm / s, and the frequency of the laser beam output by the laser emitting device is 20Hz; in step S2, when a molten pool with a depth of 0.1mm~2mm or a width of 10mm~30mm is formed at the weld, the laser irradiation can be stopped.

[0041] Step S3. Keep workpiece 1 and workpiece 2 clamped together and let them stand; the ambient temperature during standing is room temperature 20℃~28℃, and cool until the weld temperature is lower than the melting point of workpiece 1, that is, the weld melt has solidified. The standing time in the above step S3 is generally 15s.

[0042] Step S4. Adjust the second laser power of the laser emitting device 3, start the laser emitting device 3 again, and the laser beam emitted by the laser emitting device 3 is irradiated on the weld, and the laser beam emitted by the laser emitting device 3 moves along the moving trajectory of the laser beam in S2; the second laser power in step S4 is less than the first laser power in step S2, and the second laser power makes the heat generated by the laser beam greater than or equal to the melting point of the workpiece 1. The melting point temperature of PET is 265-280°C, that is, greater than 265-280°C, to ensure that the PET material is fully melted; the second laser power makes the heat generated by the laser beam less than the decomposition temperature of the workpiece 1. The decomposition temperature of PET is 350°C, that is, less than 350°C, to avoid the decomposition of the PET material to form bubbles again. If the first welding is to form an appropriate amount of bubbles, which is conducive to the formation of the weld; the second welding needs to ensure that the plastic melts again without secondary decomposition, and the temperature is between the melting point and the decomposition point, that is, between 265-280℃ and 350℃; the melting point is the temperature at which the workpiece-material changes from solid to liquid; the decomposition point is the temperature at which the workpiece-material is decomposed. The decomposition temperature refers to the temperature at which the polymer in a viscous flow state degrades the molecular chain when the temperature rises further, and rises to the temperature at which the polymer molecular chain is significantly degraded.

[0043] The negative defocus of the first weld is -5mm to -30mm, and the negative defocus of the second weld is greater than the negative defocus of the first weld in step S1. The spot diameter is adjusted by adjusting the defocus so that the diameter of the spot is larger than the width of the weld formed after the first weld. This ensures that the weld area after the first weld can completely enter the secondary melting state, so that bubbles can be filled and gas can escape from the weld edge. In other words, the purpose of the second weld is to discharge the bubbles generated by the first weld while avoiding the generation of bubbles. The second laser power is 45W, the moving speed of the laser beam in step S4 is 4mm / s, and the frequency of the laser beam output by the laser emitting device is 20Hz; and the negative defocus of the second weld is greater than the first. The size of the spot is changed by adjusting the defocus, that is, the laser spot of the second weld should be larger than the first, so that the plastic at the weld edge formed after the first weld is melted again during the second weld. In this way, while the bubbles are filled with the re-melted plastic in the weld area, the gas inside them can escape from the re-melted weld edge.

[0044] In step S5, if all bubbles in the weld are eliminated, the laser welding is completed; if bubbles still exist in the weld, repeat steps S3-S4 until all bubbles in the weld are eliminated, and the laser welding is completed;

[0045] The use of the first laser power requires the formation of an effective welding area. The power used is relatively high, and the plastic decomposes when heated. The gas in the bubble is CO, CO2, and olefin products. After the weld temperature drops to room temperature, the internal pressure of the bubble drops below atmospheric pressure, and bubbles are generated at the same time. If the heat input is too small, although the formation of bubble defects can be avoided at this time, the weld cannot be formed because the energy input is too low. The generation of bubbles can squeeze the molten plastic to the side of the second workpiece, allowing the plastic melt to enter the microstructure of the second workpiece surface to form an anchoring effect. Therefore, the generation of bubbles is conducive to the formation of the weld. However, once the weld is formed and cooled, the bubbles will be trapped in the weld, weakening the strength of the weld. Therefore, an appropriate amount of bubbles should be encouraged to form in the weld during the welding process, and bubble defects should be eliminated after the weld is formed.

[0046] The second laser power is less than the first laser power, and the second laser power ensures that the heat generated by the laser beam is greater than or equal to the melting point of workpiece 1. Research has shown that bubbles are produced by the decomposition of plastic due to heat, and the gas within the bubbles is CO, CO2, and olefin products. After the weld temperature drops to room temperature, the internal pressure of the bubbles decreases to below atmospheric pressure. Therefore, the second weld only needs to ensure that the plastic melts without decomposing the heat input, so that the bubbles are filled due to the remelting of the plastic. Using the first laser power requires forming an effective weld area, and the power used is relatively high, which will also generate bubbles. The second laser power is needed to prevent the already formed bonding interface or workpiece 1 from degrading again and generating bubbles. The relationship between the first and second laser powers is that the second laser power is 40% to 80% of the first laser power.

[0047] Example 2

[0048] See attached Figure 1 ; The above workpiece 1 is made of PMMA material, and the workpiece 2 is made of pure titanium;

[0049] Step S1. Clamp the workpiece 1 and the workpiece 2 to be welded together by the fixture 4, so that the workpiece 1 and the workpiece 2 are subjected to uniform clamping force, and a weld is formed at the position where the workpiece 1 and the workpiece 2 meet; adjust the defocus amount and the first laser power of the laser emitting device 3; the fixture 4 used is as follows: Figure 1 As shown, the clamp 4 applies up and down forces to clamp the workpiece 1 and the workpiece 2, and there are no excessive restrictions on the clamp 4.

[0050] In step S1, the method for adjusting the first laser power is to conduct a trial weld, adjusting the parameters so that the welding process can produce a connection with an appropriate amount of bubbles. Experimental research results show that bubbles are formed due to the decomposition of plastic due to heat. If the heat input is too small, although the formation of bubble defects can be avoided, the energy input is too low and a weld cannot be formed or the strength of the joint between the two does not meet the requirements. The generation of bubbles can squeeze the molten plastic toward the side of the second workpiece, allowing the plastic melt to enter the microstructure of the second workpiece surface to form an anchoring effect. Therefore, the generation of bubbles is conducive to the formation of the weld. However, once the weld is formed and cooled, the bubbles will be trapped in the weld, weakening the strength of the weld. Therefore, the formation of an appropriate amount of bubbles in the weld should be encouraged during the welding process, and the bubble defects should be eliminated after the weld is formed. Since the second workpiece is made of pure titanium, the general welding temperature is 750°C.

[0051] Step S2. Start the laser emitting device 3. The laser beam emitted by the laser emitting device 3 is irradiated on the weld and moves along the preset weld until a molten pool is formed at the weld, and then the laser irradiation is stopped; the above-mentioned first laser power is 60W, and the defocus amount is adjusted to -5mm~-30mm. The moving speed of the laser beam in step S2 is 3mm / s, and the frequency of the laser beam output by the laser emitting device is 20Hz; in step S2, when a molten pool with a depth of 0.1mm~2mm or a width of 10mm~30mm is formed at the weld, the laser irradiation can be stopped.

[0052] Step S3. Keep workpiece 1 and workpiece 2 clamped together and let them stand; the ambient temperature during standing is room temperature 20℃~28℃, and cool until the weld temperature is lower than the melting point of workpiece 1, that is, the weld melt has solidified. The standing time in the above step S3 is generally 15s.

[0053] Step S4. Adjust the second laser power of the laser emitting device 3, start the laser emitting device 3 again, and the laser beam emitted by the laser emitting device 3 is irradiated on the weld, and the laser beam emitted by the laser emitting device 3 moves along the moving trajectory of the laser beam in S2; the second laser power in step S4 is less than the first laser power in step S2, and the second laser power makes the heat generated by the laser beam greater than or equal to the melting point of the workpiece 1. The melting point temperature of PMMA is about 130-140°C, that is, greater than 130°C to ensure that PMMA is fully melted; the second laser power makes the heat generated by the laser beam less than the temperature at which the workpiece 1 decomposes. The decomposition temperature of PMMA material is about 270°C, that is, less than 270°C, to avoid the decomposition of PMMA material to form bubbles again. If the first welding is to form an appropriate amount of bubbles, which is conducive to the formation of the weld; the second welding needs to ensure that the plastic melts again without secondary decomposition, and the temperature is between the melting point and the decomposition point, that is, between 130-140℃ and 270℃; the melting point is the temperature at which the workpiece-material changes from solid to liquid; the decomposition point is the temperature at which the workpiece-material is decomposed. The decomposition temperature refers to the temperature at which the polymer in a viscous flow state degrades the molecular chain when the temperature rises further, and rises to the temperature at which the polymer molecular chain is significantly degraded.

[0054] The negative defocus of the first weld is -5mm to -30mm, and the negative defocus of the second weld is greater than the negative defocus of the first weld in step S1. The spot diameter is adjusted by adjusting the defocus so that the diameter of the spot is larger than the width of the weld formed after the first weld. This ensures that the weld area after the first weld can completely enter the secondary melting state, so that bubbles can be filled and gas can escape from the weld edge. In other words, the purpose of the second weld is to discharge the bubbles generated by the first weld while avoiding the generation of bubbles. The second laser power is 45W, the moving speed of the laser beam in step S4 is 4mm / s, and the frequency of the laser beam output by the laser emitting device is 20Hz; and the negative defocus of the second weld is greater than the first. The size of the spot is changed by adjusting the defocus, that is, the laser spot of the second weld should be larger than the first, so that the plastic at the weld edge formed after the first weld is melted again during the second weld. In this way, while the bubbles are filled with the re-melted plastic in the weld area, the gas inside them can escape from the re-melted weld edge.

[0055] In step S5, if all bubbles in the weld are eliminated, the laser welding is completed; if bubbles still exist in the weld, repeat steps S3-S4 until all bubbles in the weld are eliminated, and the laser welding is completed;

[0056] The use of the first laser power requires the formation of an effective welding area. The power used is relatively high, and PMMA decomposes when heated. The gas in the bubbles is CO, CO2, and olefin products. After the weld temperature drops to room temperature, the internal pressure of the bubbles decreases, below atmospheric pressure, and bubbles are generated at the same time. If the heat input is too small, although the formation of bubble defects can be avoided at this time, the weld cannot be formed because the energy input is too low. The generation of bubbles can squeeze the molten PMMA to the side of the second workpiece, allowing the PMMA melt to enter the microstructure of the second workpiece surface to form an anchoring effect. Therefore, the generation of bubbles is conducive to the formation of the weld. However, once the weld is formed and cooled, the bubbles will be trapped in the weld, weakening the strength of the weld. Therefore, an appropriate amount of bubbles should be encouraged to form in the weld during the welding process, and bubble defects should be eliminated after the weld is formed.

[0057] The second laser power is less than the first laser power, and the second laser power ensures that the heat generated by the laser beam is greater than or equal to the melting point of workpiece 1. Research has shown that bubbles are produced by the decomposition of PMMA due to heat, and the gases within the bubbles are CO, CO2, and olefin products. After the weld temperature drops to room temperature, the internal pressure of the bubbles decreases to below atmospheric pressure. Therefore, the second weld only needs to ensure that the PMMA melts without decomposing the heat input, so that the bubbles are filled due to the remelting of the PMMA. Using the first laser power requires forming an effective weld area, and the power used is relatively high, which will also generate bubbles. The second laser power is needed to prevent the already formed bonding interface or workpiece 1 from degrading again and generating bubbles. The relationship between the first and second laser powers is that the second laser power is 40% to 80% of the first laser power.

[0058] The present application addresses the problem of bubbles during the welding process of polymer materials (or plastics) and lightweight metals (or metal alloys / ceramics). During the first welding, a specific defocus amount, frequency and first laser power are set to generate bubbles and form an effective welding area. During the second welding, a specific defocus amount, frequency and first laser power are set so that the plastic at the edge of the weld formed after the first welding is melted again during the second welding. In this way, while the bubbles are filled with the re-melted plastic in the weld area, the gas inside them can escape from the re-melted weld edge, which not only ensures the welding strength but also avoids the influence of bubbles on the weld, thus effectively solving the welding problem between plastic and metal.

[0059] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for welding plastic and metal, characterized in that: The following steps are involved: S1: clamping workpiece 1 and workpiece 2 to be welded, forming a weld at the contact position between workpiece 1 and workpiece 2; adjusting the defocus amount, frequency and first laser power of the laser emitting device; workpiece 1 is plastic, and workpiece 2 is metal; S2 starts the laser emitting device, and the laser beam emitted by the laser emitting device irradiates the weld and moves along the preset weld until a molten pool is formed at the weld, and then stops laser irradiation; S3: keeping the workpiece 1 and the workpiece 2 in a clamped state and allowing them to cool; S4 adjusts the second laser power of the laser emitting device, starts the laser emitting device again, irradiates the laser beam emitted by the laser emitting device on the weld, and moves the laser beam emitted by the laser emitting device along the moving trajectory of the laser beam in step S2; If the bubbles in the weld are completely eliminated in step S5, the laser welding is completed; if there are still bubbles in the weld, repeat steps S3-S4 until the bubbles in the weld are completely eliminated, and the laser welding is completed; The second laser power in step S4 is less than the first laser power in step S2, and the second laser power makes the heat generated by the laser beam greater than or equal to the melting point of the workpiece 1, and the second laser power makes the heat generated by the laser beam less than the temperature at which the workpiece 1 decomposes.

2. The method for welding plastic and metal according to claim 1, characterized in that: The negative defocus amount of the second welding in step S4 is greater than the negative defocus amount of the first welding in step S1 , and the negative defocus amount of the first welding is -5 mm to -30 mm.

3. The method for welding plastic and metal according to claim 2, characterized in that: In the step S1, the first laser power is adjusted so that a connection can be produced with an appropriate amount of bubbles during the welding process.

4. The method for welding plastic and metal according to claim 3, characterized in that: In step S2, when a molten pool with a depth of 0.1 mm to 2 mm or a width of 10 mm to 30 mm is formed at the weld, the laser irradiation can be stopped.

5. The method for welding plastic and metal according to claim 4, characterized in that: In step S3, the ambient temperature during the static state is room temperature (20° C. to 28° C.), and the weld is cooled until the weld temperature is lower than the melting point of the workpiece 1, that is, the weld melt has solidified.

6. The method for welding plastic and metal according to claim 5, characterized in that: The second laser power is 40% to 80% of the first laser power.

7. The method for welding plastic and metal according to claim 6, characterized in that: In step S2, the moving speed of the laser beam is 1 mm / s to 3 mm / s, and in step S4, the moving speed of the laser beam is 4 mm / s to 7 mm / s.

8. The method for welding plastic and metal according to claim 7, characterized in that: In step S2, the laser emitting device outputs a laser beam at a frequency of 20 Hz to 40 Hz.

9. The method for welding plastic and metal according to claim 1, characterized in that: In step S4, the laser emitting device outputs a laser beam at a frequency that is the same as that in step S2.

10. The method for welding plastic and metal according to claim 1, characterized in that: In step S5, bubble defects are detected by online ultrasonic testing.

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