Welding processing method for automobile galvanized sheet reinforced by graphene / copper foil

Abstract

The invention provides a graphene / copper foil reinforced automobile galvanized sheet welding processing method which comprises the following steps: carrying out surface treatment on a galvanized steel sheet to remove oil stains and impurities on the surface; the preparation method comprises the following steps: adding graphene nanoparticles into an acetone solution, uniformly stirring and then vibrating and dispersing to obtain reinforced phase paste; the reinforcing phase paste is evenly coated on the surface of a welding piece, drying treatment is carried out, and the welding piece is a copper foil; the dried welding piece is placed between two galvanized steel sheets subjected to surface treatment, U-MIG welding is conducted, natural cooling is conducted after welding is completed, U-MIG welding is a welding method that transverse ultrasonic vibration is applied through an ultrasonic generator in a traditional MIG welding process, and specifically, under the welding process, the welding piece is subjected to U-MIG welding; the graphene and the copper foil are used as reinforcing phases to improve welding defects of the galvanized steel sheet and microcosmic grains of a welding joint in the welding process, and the performance of the composite welding joint is further improved.

Description

Technical Field

[0001] This invention belongs to the field of automotive galvanized sheet welding technology, specifically relating to a welding method for automotive galvanized sheets reinforced with graphene / copper foil. Background Technology

[0002] Automotive lightweighting is a concept that promotes energy conservation, reduces emissions, and protects the environment. It refers to reducing the weight of a vehicle while ensuring its safety performance and overall structural quality, thereby reducing fossil fuel consumption and vehicle emissions. The most effective measures for automotive lightweighting primarily involve using lightweight materials such as aluminum, magnesium, plastics, and fiberglass. Nevertheless, steel remains the primary choice for the automotive manufacturing industry due to its low cost and good formability. The corrosion resistance of materials has become an essential performance requirement for automakers. When galvanized steel is coated, atmospheric carbon dioxide, oxygen, and water react with the zinc to form a dense 6-30 μm oxide film, covering the steel surface and preventing corrosion. Simultaneously, galvanized steel sheets may undergo electrochemical corrosion in the external environment. Zinc's electrode potential (-0.762V) is lower than iron's (-0.44V), meaning zinc corrodes before iron, and the zinc layer acts as the anode, providing electrochemical protection to the steel. However, the galvanized layer presents welding difficulties during the welding process. This is mainly because zinc's boiling point (906℃) is much lower than steel's melting point (1500℃). As the base material melts, a large amount of the galvanized layer volatilizes at high temperatures. Furthermore, the rapid solidification of the weld pool means that steam cannot escape from the weld in time, leading to welding defects such as undercut, slag inclusions, porosity, and spatter. These defects severely affect the quality of the weld joint, causing reduced joint strength and premature failure.

[0003] Metal Inert Gas Welding (MIG) is an arc-based welding process that uses an inert gas to protect the welding materials from oxidation. MIG welding offers advantages such as high production efficiency, low cost, ease of automation, wide applicability, and minimal weld deformation, making it widely used in various manufacturing industries.

[0004] Traditional MIG welding technology has several drawbacks, such as the instability of the welding arc and uneven heat source distribution. These defects severely hinder the application and development of this technology. Particularly in the automotive industry, for materials like galvanized steel sheets, the volatilization of zinc during welding can lead to defects such as porosity and undercut, significantly impacting the quality of the weld joint, reducing its strength, and even causing premature failure. Summary of the Invention

[0005] Based on this, the present invention provides a welding process for automotive galvanized sheet metal reinforced with graphene / copper foil, which aims to avoid welding defects, enhance welding strength, and improve the quality and performance of welded parts.

[0006] A first aspect of this invention provides a welding process for automotive galvanized sheet metal reinforced with graphene / copper foil, comprising the following steps: The galvanized steel sheet undergoes surface treatment to remove oil and impurities from the surface; Graphene nanoparticles were added to an acetone solution, stirred until homogeneous, and then dispersed by vibration to obtain a reinforced phase paste. A reinforcing paste is uniformly applied to the surface of the weldment and then dried, wherein the weldment is a copper foil. The dried weldment is placed between two surface-treated galvanized steel plates and subjected to U-MIG welding. After welding, it is allowed to cool naturally. U-MIG welding is a welding method in which transverse ultrasonic vibration is applied by an ultrasonic generator in the traditional MIG welding process.

[0007] Furthermore, the graphene nanoparticles account for 2% to 6% of the total mass of the acetone solution.

[0008] Furthermore, in the step of uniformly applying the reinforcing phase paste to the surface of the weldment and drying it, wherein the weldment is a copper foil, the application width of the reinforcing phase paste is consistent with the width of the weldment and is greater than the weld weld width.

[0009] Furthermore, during the U-MIG welding process, the welding parameters of the welding machine were set as follows: welding current of 120A~145A, welding voltage of 22V~23V, argon flow rate of 15L / min, and welding speed of 5.0mm / s.

[0010] Furthermore, during the U-MIG welding process, the parameters of the ultrasonic generator are: energy 1000W, voltage 220V, current 0.6A, and frequency 25KHz.

[0011] Furthermore, the concentration of the acetone solution is greater than 99.5%.

[0012] Furthermore, the thickness of the galvanized steel sheet is 0.8mm to 2mm.

[0013] Compared with the prior art, implementing the present invention has the following beneficial effects: 1. Under the same welding process parameters, adding graphene as a nano-reinforcing phase can not only adsorb the gas in the weld and reduce the generation of porosity, but also play a role in dispersion strengthening and grain refinement, thus refining the grain of the weld joint. 2. Copper increases thermal conductivity, accelerates weld cooling, increases undercooling, promotes spontaneous nucleation, and increases and refines grain number. In addition, Cu forms Fe-Cu solid solution in galvanized steel sheet, which plays a solid solution strengthening role. 3. The addition of ultrasound promotes droplet transfer and stabilizes the arc, making the welding heat source more concentrated and increasing the weld depth-to-width ratio. Attached Figure Description

[0014] Figure 1 A flowchart of a welding process for automotive galvanized sheet metal reinforced with graphene / copper foil provided by the present invention; Figure 2 A schematic diagram of the structure for welding and processing galvanized sheet metal for automobiles; Figure 3 The images show the macroscopic weld morphology and local microstructure of the weld joint in Comparative Example 1. Figure 4 The images show the macroscopic weld morphology and local microstructure of the weld joint in Embodiment 1 of the present invention. Figure 5 The X-ray diffraction pattern of the welded joint in Comparative Example 1; Figure 6 This is an X-ray diffraction pattern of the welded joint in Embodiment 1 of the present invention; Figure 7 The diagram shows the mechanical properties of the welded joints in Comparative Example 1 and Embodiment 1 of the present invention.

[0015] The following detailed embodiments will be further described in conjunction with the above-mentioned accompanying drawings. Detailed Implementation

[0016] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0017] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] Please see Figure 1 The present invention provides a flowchart of a welding process for automotive galvanized sheet metal reinforced with graphene / copper foil, wherein the preparation method specifically includes the following steps: Step S01: Perform surface treatment on the galvanized steel sheet to remove oil and impurities from the surface.

[0020] Specifically, the surface of the galvanized steel sheet can be wiped with a cotton ball soaked in alcohol to remove surface oil and impurities. The thickness of the galvanized steel sheet is 0.8mm to 2mm, for example, 0.8mm, 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm or 2mm, but not limited to these.

[0021] Step S02: Add graphene nanoparticles to an acetone solution, stir until homogeneous, and then vibrate to disperse to obtain a reinforced phase paste.

[0022] In this embodiment of the invention, graphene nanoparticles are added to an acetone solution (concentration greater than 99.5%), stirred uniformly with a glass rod, and then dispersed by ultrasonic vibration to obtain a reinforced paste. The graphene nanoparticles constitute 2% to 6% of the total mass of the acetone solution. For example, the proportion of graphene nanoparticles in the total mass of the acetone solution may be 2%, 3%, 4%, 5%, or 6%, but is not limited to these.

[0023] Step S03: The reinforcing phase paste is uniformly applied to the surface of the weldment and then dried. The weldment is a copper foil.

[0024] It should be noted that the width of the reinforcing paste coating is consistent with the width of the weldment; that is, the width is determined by the width of the copper foil used, and the width is greater than the weld weld width. Drying is performed in a vacuum drying oven.

[0025] Step S04: Place the dried weldment between two surface-treated galvanized steel plates and perform U-MIG welding. Allow it to cool naturally after welding.

[0026] Understandably, the two sides of the weldment are coated with a reinforcing paste and placed between two surface-treated galvanized steel sheets. The two galvanized steel sheets abut against the weldment coated with the reinforcing paste. After placement, U-MIG welding is performed. U-MIG welding is a welding method that uses an ultrasonic generator to apply transverse ultrasonic vibration in the traditional MIG welding process. Please refer to [link to relevant documentation]. Figure 2 This is a schematic diagram of the structure for welding galvanized steel sheets for automobiles. It includes a working platform 1, a MIG welding torch 2, and an ultrasonic generator 3. The principle is to convert the high-frequency signal generated by the ultrasonic generator into mechanical force, transmit lateral vibration to the welding torch, and use ultrasound to promote the transition of molten droplets and stabilize the arc to improve the weldability of the galvanized steel sheet and improve the weld quality of the galvanized steel sheet.

[0027] Specifically, the welding parameters of the welding machine are set as follows: welding current 120A~145A, welding voltage 22V~23V, argon flow rate 15L / min, welding speed 5.0mm / s. In addition, the parameters of the ultrasonic generator are: energy 800W~1000W, voltage 220V, current 0.6A, frequency 25KHz~28KHz, and ultrasonic generator amplitude 0.1mm~0.2mm.

[0028] To facilitate understanding of the present invention, several embodiments are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete.

[0029] Example 1 In Embodiment 1 of this invention, a welding process for automotive galvanized sheet metal reinforced with graphene / copper foil is provided. The base materials for welding are SGCC type hot-dip galvanized steel sheets, each with dimensions of 200mm × 50mm × 1mm. The welded parts (copper foil) have dimensions of 100mm × 20mm × 0.05mm. Specifically, the process includes: (1) Surface treatment steps. Wipe the surface of the galvanized steel sheet with a cotton ball soaked in alcohol to remove oil and impurities.

[0030] (2) Preparation of the reinforcing phase. 5.5g of graphene nanoparticles were added to an acetone solution (concentration greater than 99.5%), stirred evenly with a glass rod, and then placed in an ultrasonic instrument for vibration dispersion. The mass ratio of graphene nanoparticles to acetone solution was 1:20.

[0031] (3) Surface coating step. Apply the reinforcing phase paste evenly to the surface of the weldment with a flat brush. The coating width is 20 mm. Place it in a vacuum drying oven to dry. After drying, place the copper foil between the two steel plates.

[0032] (4) Steel plate welding steps. The welding parameters of the welding machine are set as follows: welding current is 140A, welding voltage is 22V, argon flow rate is 15L / min, welding speed is 5.0mm / s. The steel plate is placed on the welding platform for U-MIG welding. The parameters of the ultrasonic generator are: energy 1000W, ultrasonic voltage 220V, ultrasonic current 0.6A, frequency 25KHz, ultrasonic generator amplitude 0.2mm. The ultrasonic generator applies transverse ultrasonic vibration to the MIG welding torch to achieve reliable welding of the weld size during the welding process. After welding, it is allowed to cool naturally.

[0033] Example 2 The difference between the preparation method in Example 2 and that in Example 1 is that 2.5g of graphene nanoparticles are added to an acetone solution (concentration greater than 99.5%), the mass ratio of graphene nanoparticles to acetone solution is 1:20, and the parameters of the ultrasonic generator are: energy 800W, frequency 28KHz.

[0034] Example 3 The difference between the preparation method in Embodiment 3 and that in Embodiment 1 is that the specifications of the welded part (copper foil) are 100mm×20mm×0.1mm and the amplitude of the ultrasonic generator is 0.1mm.

[0035] Example 4 The difference between the preparation method in Example 4 and that in Example 1 is that 2.5g of graphene nanoparticles are added to an acetone solution (concentration greater than 99.5%), the mass ratio of graphene nanoparticles to acetone solution is 1:20, the specifications of the welded part (copper foil) are 100mm×20mm×0.1mm, and the parameters of the ultrasonic generator are: energy 800W, frequency 28KHz, and ultrasonic generator amplitude 0.1mm.

[0036] Comparative Example 1 Comparative Example 1 proposes a welding process for automotive galvanized sheet metal. The difference from Example 1 is that graphene nanoparticles and copper foil are not used. Instead, after surface treatment of the galvanized steel sheet, the galvanized steel sheet is fixed to the welding base fixture by overlapping, and then welding is performed.

[0037] Each welded joint from Examples 1 to 4 and Comparative Example 1 was subjected to performance tests under the same conditions, and the parameters are shown in Table 1: Table 1

[0038] Figure 3 The images show the macroscopic weld morphology and local microstructure of the weld joint in Comparative Example 1. The arrows indicate the directions of Young's modulus and Vickers hardness mechanical tests. Figure 4 The images show the macroscopic weld morphology and local microstructure of the weld joint in Embodiment 1 of the present invention. The arrows indicate the directions of Young's modulus and Vickers hardness mechanical tests. Figure 5 The image shows the X-ray diffraction pattern of the welded joint in Comparative Example 1. Figure 6 This is an X-ray diffraction pattern of the welded joint in Embodiment 1 of the present invention; Figure 7 Comparative Example 1 and Example 1 of the present invention show the mechanical properties of the welded joints. It can be observed that the weld in Example 1 has a more aesthetically pleasing macroscopic morphology, is free of porosity, and has increased penetration depth. The microstructure of the weld is significantly refined and increased. The X-ray diffraction pattern no longer shows a single Fe peak. Mechanical property testing and analysis show that the Young's modulus and hardness at the corresponding locations in Example 1 are significantly higher than those in Comparative Example 1. The results indicate that adding graphene and copper foil using the U-MIG welding process can optimize the macroscopic morphology of the welded joint and improve its mechanical properties.

[0039] Furthermore, data shows that among various welding processes, changes in graphene content have the most significant impact on weld quality. With varying graphene content, the comprehensive mechanical properties of the weld microstructure increase, reaching a relative peak. Under the condition of maintaining the arc welding voltage, the ultrasonic generator energy, ultrasonic frequency, and the horizontal distance between the ultrasonic wave and the welding torch are crucial for changes in microstructure and arc welding current, thus affecting weld formation. When the distance is zero, achieving close contact, the ultrasonic generator can effectively increase welding energy, accelerating the influence of the transverse shear force of the arc welding droplet, thereby promoting rapid droplet separation and descent, accelerating the welding process transition, and achieving the expected welding plan and requirements. The optimal experimental parameters were found in Example 1 (5.5g graphene added, 0.05mm copper foil, ultrasonic power 1000W, 25KHz, arc welding current 140A).

[0040] In summary, the present invention proposes a method for welding automotive galvanized steel sheets reinforced with graphene / copper foil. This method involves surface treatment of the galvanized steel sheet to remove surface oil and impurities; adding graphene nanoparticles to an acetone solution, stirring until uniform, and then vibrating to disperse the particles to obtain a reinforcing phase paste; uniformly applying the reinforcing phase paste to the surface of the weldment and drying it, wherein the weldment is copper foil; placing the dried weldment between two surface-treated galvanized steel sheets for U-MIG welding; and allowing it to cool naturally after welding. U-MIG welding is a welding method that uses an ultrasonic generator to apply transverse ultrasonic vibration in the traditional MIG welding process. Specifically, in this welding process, graphene and copper foil act as reinforcing phases to improve welding defects and micrograin structure of the weld joint, further enhancing the performance of the composite weld joint.

[0041] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for welding a galvanized sheet for an automobile with reinforcement of graphene / copper foil, characterized by, The method comprises the following steps: Surface treatment is performed on the galvanized steel sheet to remove oil and impurities on the surface; Graphene nanoparticles are added to an acetone solution, and after stirring and uniform mixing, vibration dispersion is performed to obtain a reinforced paste; The reinforced paste is uniformly coated on the surface of a welding piece, which is a copper foil, and drying treatment is performed; The welding piece after drying treatment is placed between two surface-treated galvanized steel sheets, and U-MIG welding is performed, and after welding, natural cooling is performed, wherein the U-MIG welding is a welding method in which transverse ultrasonic vibration is applied to a traditional MIG welding process through an ultrasonic generator.

2. The method for welding of automotive galvanized sheet strengthened with graphene / copper foil according to claim 1, characterized in that, The mass ratio of the graphene nanoparticles to the overall acetone solution is 2% to 6%.

3. The method for welding of automotive galvanized sheet with graphene / copper foil reinforcement according to claim 1, characterized in that, In the step of uniformly coating the reinforced paste on the surface of the welding piece, which is a copper foil, and performing drying treatment, the coating width of the reinforced paste is consistent with the width of the welding piece, and the width is greater than the weld width.

4. The method for welding of automotive galvanized sheet with graphene / copper foil reinforcement according to claim 1, characterized in that, During the U-MIG welding process, the welding machine welding parameters are set as follows: welding current is 120 A to 145 A, welding voltage is 22 V to 23 V, argon flow rate is 15 L / min, and welding speed is 5.0 mm / s.

5. The method for welding of automotive galvanized sheet with graphene / copper foil reinforcement according to claim 4, characterized in that, During the U-MIG welding process, the parameters of the ultrasonic generator are as follows: energy is 1000 W, voltage is 220 V, current is 0.6 A, and frequency is 25 KHz.

6. The method for welding process of automotive galvanized sheet reinforced with graphene / copper foil according to claim 1, characterized in that, The concentration of the acetone solution is greater than 99.5%.

7. The method for welding process of automotive galvanized sheet reinforced with graphene / copper foil according to claim 1, characterized in that, The thickness of the galvanized steel sheet is 0.8 mm to 2 mm.

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