Pretreatment method of surface of aluminum alloy substrate before welding and surface structure generated by pretreatment method

Abstract

The invention provides a method for carrying out surface pretreatment on an aluminum alloy substrate before welding and a surface structure of the aluminum alloy substrate formed by the method. The method includes ionizing an inert gas using a radio frequency ion source in a discharge chamber and accelerating the ionized inert gas to obtain energy. Then, ionized inert gas is guided to the surface of the aluminum alloy substrate to remove the amorphous oxide layer and polish the surface. And reducing functional groups are formed on the surface of the aluminum alloy substrate, so that secondary oxidation is prevented. This reducing functional group is formed by ionizing a reducing gas and guiding the ionized reducing gas to the surface of the aluminum alloy substrate. The method can be applied to various welding techniques such as arc welding, TIG welding, laser welding, electron beam welding, vacuum welding or diffusion welding.

Description

Technical Field

[0001] The invention relates to a pretreatment of a metal surface and a surface structure produced by the pretreatment, in particular to a method for pretreatment of the surface of an aluminum alloy substrate before welding and the surface structure of the aluminum alloy substrate. Background Art

[0002] Aluminum alloys are widely used in a variety of industries due to their high strength and lightweight properties, good corrosion resistance, and excellent thermal and electrical conductivity. However, welding aluminum alloys presents unique challenges. One of the main issues is the formation of an amorphous oxide layer on the surface of aluminum alloys. This oxide layer interferes with the welding process and causes the strength of the weld joint to decrease. In addition, even if the oxide layer is removed, secondary oxidation may still occur on the surface of aluminum alloys when exposed to an oxidizing environment. This secondary oxidation also interferes with the welding process and reduces the strength of the weld. In addition, the surface roughness of aluminum alloys can affect the quality of the weld. Smoother surfaces result in cleaner and stronger welds. However, achieving the required surface roughness can be challenging.

[0003] Therefore, an effective method is needed to pretreat the aluminum alloy surface before welding, which method should be able to remove the oxide layer, prevent secondary oxidation and achieve the required surface roughness. How to solve the above problems is worth considering by those with general knowledge in this field. Summary of the invention

[0004] In order to solve the above problems, an object of the present invention is to provide a method for pretreating the surface of an aluminum alloy substrate before welding and a surface structure of the aluminum alloy substrate.

[0005] Based on the above and other purposes, the present invention provides a method for surface pretreatment of an aluminum alloy substrate before welding. The method comprises the following steps: ionizing an inert gas using a radio frequency ion source in a discharge chamber, accelerating the ionized inert gas to obtain energy, directing the ionized inert gas to the surface of the aluminum alloy substrate, removing an amorphous oxide layer and polishing the surface of the aluminum alloy substrate, and forming a reducing functional group on the surface of the aluminum alloy substrate to prevent secondary oxidation. The reducing functional group is formed by ionizing the reducing gas and directing the ionized reducing gas to the surface of the aluminum alloy substrate.

[0006] In some embodiments, the ionized inert gas (i.e., the first inert gas and the second inert gas) is selected from the group consisting of helium (He), neon (Ne), and argon (Ar). In other embodiments, the reducing gas is selected from the group consisting of hydrogen chloride, methane, and ammonia. In other embodiments, the process parameters of each step are selected from the group consisting of current 100-1800 mA, voltage 100-1500 V, gas flow rate 5-200 sccm, and process pressure 1.0E-2-1.0E-4 Torr.

[0007] In some embodiments, a grid system is used to accelerate the ionized inert gas. In other embodiments, after the step of polishing the surface of the aluminum alloy substrate is completed, the surface roughness of the aluminum alloy substrate is between 0.01-0.04 microns. In other embodiments, the mixing ratio of the reducing gas and the inert gas is 2:98 to 30:70.

[0008] In certain embodiments, after the pretreatment is completed, the surface of the aluminum alloy substrate is suitable for the following welding methods: arc welding, TIG welding, laser welding, electron beam welding, vacuum welding or diffusion welding.

[0009] The present invention also provides a surface structure of an aluminum alloy substrate formed by the above method. In certain embodiments, the surface structure of the aluminum alloy substrate further includes forming a reducing functional group on the surface of the aluminum alloy substrate to prevent secondary oxidation. In other embodiments, the reducing functional group is selected from the group of RH or RX functional groups.

[0010] In summary, the present invention provides a novel method for surface pretreatment of an aluminum alloy substrate before welding. The method includes ionizing an inert gas, accelerating the ionized inert gas to obtain energy, directing the ionized inert gas to the surface of the aluminum alloy substrate to remove an amorphous oxide layer and polish the surface, and forming a reducing functional group on the surface of the aluminum alloy substrate to prevent secondary oxidation, and the present invention also provides a surface structure of the aluminum alloy substrate formed by the above method. The method and the resulting surface structure have multiple advantages. They can improve the weldability of the aluminum alloy substrate, enhance the quality of the subsequent welding process, and extend the service life of the welded product.

[0011] In order to achieve the above and other purposes, the present invention adopts technical means, components and their effects, and a preferred embodiment is described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The flowchart shown is a method for pretreating the surface of an aluminum alloy substrate before welding according to the present invention.

[0013] FIG. 2A to FIG. 2EDepicted are schematic diagrams of the pretreatment method of the present invention at various steps.

[0014] Figure 3 Depicted is the structure of the grid system and its role in generating the electric field for ion acceleration.

[0015] Figure 4A and Figure 4B Shown is a schematic diagram of welding of the aluminum alloy substrate after pretreatment. DETAILED DESCRIPTION

[0016] Please refer to Figure 1 , Figure 1 The flowchart shown is a method for pretreating the surface of an aluminum alloy substrate before welding according to the present invention. FIG. 2A to FIG. 2E The diagram shows the steps of the pretreatment method of the present invention. The method aims to improve the quality of the aluminum alloy substrate after welding by removing the amorphous oxide layer 102 and polishing the surface of the aluminum alloy substrate. First, as shown in step S210 and Figure 2A As shown, an untreated aluminum alloy substrate 100 is provided, and an amorphous oxide layer 102 is provided on a surface 110 thereof. Next, as shown in step S220, a first noble gas is ionized using a radio frequency ion source in a discharge chamber. In the present embodiment, the ion source uses radio frequency power to generate plasma from the first noble gas, and this process generates ions and electrons. The first noble gas can be one or a combination of helium (He), neon (Ne) and argon (Ar), and the ionization of the first noble gas results in the generation of ionized noble gas. Once the first noble gas is ionized, the method further accelerates the ionized first noble gas to obtain energy, as shown in step S230. In the present embodiment, a grid system 30 (such as Figure 3 The grid system provides an electric field to accelerate the ionized first inert gas to increase the kinetic energy of the ionized first inert gas. According to actual specific requirements, the acceleration of the ionized first inert gas can be achieved by various technologies, such as electric field or magnetic field. Then, as shown in step S240 and Figure 2B As shown, the ionized first inert gas is directed to the surface 110 of the aluminum alloy substrate 100. The high-energy ionized first inert gas interacts with the surface 110 of the aluminum alloy substrate 100 to remove the amorphous oxide layer.

[0017] In addition, as in step S250 and Figure 2CAs shown, a second inert gas is ionized, and the ionized second inert gas is guided to the surface 110 of the aluminum alloy substrate 100, and the surface 110 can be polished. In this embodiment, the bombardment time of the ionized second inert gas on the surface 110 of the aluminum alloy substrate 100 is adjusted so that the roughness of the surface 110 is within a certain range. Removing the amorphous oxide layer and polishing the surface 110 improves the state of the surface 110 of the aluminum alloy substrate 100, making it more suitable for the subsequent welding process. In addition, in this embodiment, the roughness of the surface 110 of the aluminum alloy substrate 100 is between 0.01-0.04 microns. A surface 110 that is too rough may cause poor contact during welding and affect the quality of welding. On the other hand, a surface 110 that is too smooth may hinder the formation of welding. Therefore, the inventor of this case found that when the roughness of the surface 110 of the aluminum alloy substrate 100 is between 0.01-0.04 microns, a balance can be provided, which is conducive to the formation of high-quality welding during subsequent welding. It should be noted that the process parameters of the first ionized inert gas used for polishing are usually different from the process parameters of the second ionized inert gas used for removing the amorphous oxide layer. However, the type of inert gas can be the same, such as one or a combination of helium (He), neon (Ne) and argon (Ar).

[0018] Next, as in step S260 and Figure 2D As shown, using a method similar to step S220 and step S230, the reducing gas 20 is ionized and the ionized reducing gas 20 ions are directed to the surface 110 of the aluminum alloy substrate 100 to form a protective layer 120 composed of reducing functional groups on the surface 110 of the aluminum alloy substrate 100 (as shown in step S270 and step S280). Figure 2E The purpose of this step is to prevent secondary oxidation of the substrate surface 110 so as not to affect the effect of the subsequent welding process. The reducing functional group is formed by ionizing the reducing gas 20 and directing the ionized reducing gas 20 to the surface 110 of the aluminum alloy substrate 100. In this embodiment, the reducing gas 20 can be selected from the group consisting of hydrogen chloride, methane and ammonia.

[0019] Through the above steps, a pre-treated aluminum alloy substrate 100 can be formed, which can ensure that the surface 110 of the aluminum alloy substrate 100 is in an optimal state to form a strong and reliable welding joint. The specific selection of the inert gas and the reducing gas, as well as the process parameters, may vary according to specific requirements, which will be described in detail in the subsequent embodiments.

[0020] In the method of pretreating the surface 110 of the aluminum alloy substrate 100, the selection of the type of inert gas to be ionized is of certain importance because the selected inert gas can affect various parameters such as the energy, size and interaction of the ions with the substrate.

[0021] In this embodiment, we choose to use helium (He), neon (Ne) and argon (Ar) as inert gases. Each gas has its own unique advantages and considerations. For example, helium is the lightest inert gas and its ions have lower energy. This property enables it to more thoroughly remove the amorphous oxide layer and polish the surface of the aluminum alloy substrate more finely. Neon is heavier than helium and its ions have higher energy, which can increase the efficiency of removing the amorphous oxide layer on the surface of the substrate. However, high-energy ions need to be carefully controlled to avoid potential damage to the substrate. Argon is the heaviest of the three inert gases and its ions have the highest energy. Therefore, it is most efficient in removing the amorphous oxide layer, but it is also most likely to cause damage to the substrate.

[0022] In summary, for the selection of inert gas, we can consider the specific requirements of the pretreatment process. When selecting an inert gas, factors such as the thoroughness of oxide layer removal, the degree of substrate polishing, and the acceptable risk of substrate damage must be considered. Helium, neon, and argon all have their own unique advantages, so we can choose to mix these inert gases to combine their respective advantages.

[0023] In addition, in the method of pre-treating the surface 110 of the aluminum alloy substrate 100, the selection of reducing gas has an impact on the effect of preventing secondary oxidation. In this embodiment, we selected hydrogen chloride, methane and ammonia as reducing gases, which can be ionized and directed to the surface of the aluminum alloy substrate to form reducing functional groups such as RH or RX functional groups, where R is an oxygen-containing functional group, such as -OH, -CH2OH, etc., and RX represents a halogen-containing functional group, such as -CH2Cl, -CHCl2. Wherein "-" represents an active bond bound to the surface of the aluminum alloy metal, thereby forming a functional group protective film layer to protect the metal surface from oxidation.

[0024] The choice of reducing gas is influenced by many factors, such as the desired reducing functional group characteristics, the specific requirements of the subsequent welding process, and the availability and cost of the gas. Hydrogen chloride, methane and ammonia each have their own unique advantages and can be selected and applied according to the specific needs of the pretreatment process.

[0025] In the method for pretreating the surface of an aluminum alloy substrate, process parameters include current, voltage, gas flow rate and treatment pressure, which determine the energy of the ionized gas, the rate of ionization and reduction process, and the quality of the surface of the aluminum alloy substrate after treatment. In the present embodiment, the current parameter ranges from 100mA to 1800mA. The current level can affect the ion density in the gas, and a higher current will generate a denser plasma. The voltage parameter can range from 100V to 1500V, which is applied to accelerate the ionized gas toward the aluminum alloy substrate, and a higher voltage will produce ions with higher energy. The gas flow rate parameter ranges from 5sccm to 200sccm, which determines the amount of gas entering the discharge chamber, and a higher flow rate provides more gas for ionization. The treatment pressure can range from 1.0E-2Torr to 1.0E-4Torr. Throughout the process, the discharge chamber is maintained at this pressure. The treatment pressure affects the mean free path of the ions, which in turn affects their interaction with the substrate surface. Lower pressures may produce ions with higher energy because the opportunity for collision cooling is reduced.

[0026] In the method for pre-treating the surface of the aluminum alloy substrate, the grid system 30 is used to accelerate the movement of the ionized inert gas (ie, the first inert gas and the second inert gas mentioned above). Figure 3 The grid system 30 is generally composed of at least one closely parallel mesh plate 32 (a metal plate with multiple grids thereon) for creating an electric field to accelerate the ions generated by the discharge chamber. Figure 3 Take three screens 32 as an example. In actual operation, the number of screens 32 can be increased or decreased as needed, and each screen 32 can also have different potentials. In other words, the ionized inert gas 10 gains energy when moving in the electric field created by the grid system, thereby increasing their speed. The design of the grid system 30 will affect the uniformity of the electric field, thereby affecting the energy distribution of the ions. A well-designed grid system 30 can ensure a uniform electric field distribution, thereby obtaining consistent ion energy, so as to uniformly remove the oxide layer on the surface of the aluminum alloy substrate and uniformly form reducing functional groups on the surface of the aluminum alloy substrate. In addition, it is worth mentioning that when the thickness of the screen 32 is thicker or the number is more, when the gas passes through the grid system 30, the ion-containing gas scattered to the side will hit the mesh wall and correct its direction, and finally will move in a path close to the vertical grid direction, so the design of the grid system 30 can also be used to guide the direction of the ion-containing gas.

[0027] There are several advantages to using a grid system 30 to accelerate the ionized gas. First, it allows for controlled and consistent acceleration of the ions. Second, it provides a way to manage the energy and direction of the ions, thereby controlling the interaction of the ions with the surface of the aluminum alloy substrate. Furthermore, it makes it possible to fine-tune the process according to the specific requirements of the pretreatment and subsequent welding process.

[0028] In addition, in one embodiment, the relative ratio of reducing gas to inert gas is, for example, between 2:98 and 30:70. At the lower end of the range (2:98), the amount of reducing gas is less relative to the inert gas, and this configuration is suitable for situations where a milder reduction process is required. At the higher end of the range (30:70), the amount of reducing gas is larger relative to the inert gas, and this configuration can be used for situations where a more powerful reduction process is required. By adjusting the ratio of reducing gas to inert gas, the surface pretreatment process can be fine-tuned.

[0029] After the surface pretreatment of the aluminum alloy substrate is completed, the substrate can be welded with other metals. Figure 4A As shown, two aluminum alloy substrates 100, 200 are placed together and prepared for welding. The surface of the pre-treated aluminum alloy substrate 110 is in contact with the aluminum alloy substrate 200. Then, as shown in FIG. Figure 4B As shown, two aluminum alloy substrates 100 and 200 are welded together. In this embodiment, the surface of the aluminum alloy substrate 200 welded with the aluminum alloy substrate 100 has also undergone the above-mentioned pretreatment process, which helps to ensure that the two surfaces to be connected are in the best welding state, thereby improving the welding quality. In addition, it is worth noting that the welding ability of the pretreated aluminum alloy substrate 100 is not limited to other aluminum alloys. In fact, the pretreated aluminum alloy substrate 100 can be welded with various other metals. The specific method of selecting other metals depends on the application requirements and can include steel, copper, and even other non-ferrous alloys. Therefore, the surface pretreatment process described improves the versatility of the aluminum alloy substrate, enabling it to be applied in various welding scenarios.

[0030] In this embodiment, welding methods compatible with the pretreated aluminum alloy substrate include arc welding, TIG (tungsten argon) welding, laser welding, electron beam welding, vacuum welding and diffusion welding. Arc welding is a widely used welding method that involves generating an arc between an electrode and a workpiece (in this example, an aluminum alloy substrate). The heat generated by the arc melts the workpiece and the electrode, forming a weld when the molten material cools. TIG welding is a welding method that uses a tungsten electrode and an inert shielding gas, while laser welding uses a high-intensity laser to melt and fuse the materials. Electron beam welding uses a high-speed electron beam to generate the heat required for welding, while vacuum welding is a welding process performed in a vacuum environment. Diffusion welding involves applying pressure and heat to the materials to be welded, causing atoms to diffuse at the interface.

[0031] In summary, the method of surface pretreatment of aluminum alloy substrate can form a unique surface structure, namely Figure 2E The protective layer 120 surface structure with reducing functional groups shown in the figure enhances the weldability of the aluminum alloy substrate. The first feature of this surface structure is the removal of the amorphous oxide layer. This oxide layer is usually present on the surface of the aluminum alloy, which may affect the quality of welding. By guiding the ionized inert gas to the substrate surface, the oxide layer can be effectively removed and the surface can be smoothed. In this embodiment, the surface roughness of the aluminum alloy substrate can be controlled within the range of 0.01-0.04 microns, and this surface roughness helps to form high-quality welding.

[0032] In addition, the second feature of the surface structure is that a protective layer with reducing functional groups is formed on the substrate surface to prevent the occurrence of secondary oxidation. By ionizing the reducing gas and directing it to the surface of the aluminum alloy substrate, a protective layer with reducing functional groups can be formed, which can effectively prevent the formation of secondary oxidation, which may otherwise affect the quality of the weld. By inhibiting secondary oxidation, the protective layer with reducing functional groups ensures that the surface of the aluminum alloy substrate remains in an ideal welding state, thereby improving the weldability of the aluminum alloy substrate.

[0033] The invention is described above, but it is not intended to limit the scope of the patent rights claimed by the invention. Any changes or modifications made by those skilled in the art without departing from the spirit or scope of this patent shall be considered as equivalent changes or designs completed under the spirit disclosed by the invention and shall be included in the claims of the invention.

Claims

1. A method for pretreating the surface of an aluminum alloy substrate before welding, characterized in that: The method includes: (a) ionizing a first noble gas in a discharge chamber using a radio frequency ion source; (b) accelerating the ionized first inert gas to obtain energy; (c) directing the ionized first inert gas to a surface of an aluminum alloy substrate to remove an amorphous oxide layer; (d) ionizing a second noble gas and accelerating the ionized second noble gas; (e) directing the ionized second inert gas to the surface of the aluminum alloy substrate to polish the surface of the aluminum alloy substrate; and (f) forming reducing functional groups on the surface of the aluminum alloy substrate to prevent secondary oxidation; The reducing functional group is formed by ionizing a reducing gas and directing the ionized reducing gas to the surface of the aluminum alloy substrate.

2. The method according to claim 1, characterized in that The first inert gas and the second inert gas are selected from the group consisting of helium (He), neon (Ne) and argon (Ar).

3. The method according to claim 1, characterized in that The reducing gas is selected from the group consisting of hydrochloride, methane and a nitrogen-hydrogen mixture.

4. The method according to claim 1, characterized in that The process parameters of each step are selected from the group consisting of a current of 100-1800 mA, a voltage of 100-1500 V, a gas flow rate of 5-200 sccm, and a process pressure of 1.0E-2-1.0E-4 Torr.

5. The method according to claim 1, characterized in that In step (b), a grid system is used to accelerate the ionized inert gas.

6. The method according to claim 1, characterized in that After step (c) is completed, the surface roughness of the aluminum alloy substrate is between 0.01-0.04 microns.

7. The method according to claim 1, characterized in that After the surface of the aluminum alloy substrate is pre-treated, it is suitable for the following welding methods: arc welding, TIG welding, laser welding, electron beam welding, vacuum welding, or diffusion welding.

8. A surface structure of an aluminum alloy substrate, characterized in that It is formed by the following steps: (a) ionizing a first inert gas and directing the ionized first inert gas to a surface of an aluminum alloy substrate to remove an amorphous oxide layer; (b) ionizing a second inert gas and directing the ionized second inert gas to the surface of the aluminum alloy substrate to polish the surface of the aluminum alloy substrate to a surface roughness between 0.01 μm and 0.04 μm; (c) ionizing a reducing gas and directing the ionized reducing gas to the surface of the aluminum alloy substrate to form reducing functional groups on the surface of the aluminum alloy substrate to prevent secondary oxidation.

9. The surface structure of the aluminum alloy substrate according to claim 8, characterized in that: The first inert gas and the second inert gas are selected from the group consisting of helium (He), neon (Ne) and argon (Ar).

10. The surface structure of the aluminum alloy substrate according to claim 8, characterized in that: The reducing functional group is selected from the group consisting of RH and RX functional groups.

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