A cleaning agent and method for removing laser welding spots on the surface of NdFeB

Abstract

The present invention discloses a cleaning agent and method for removing laser welding spots on the surface of NdFeB. The cleaning agent is obtained by mixing 20% ​​to 25% nitric acid, 15% to 20% hydrofluoric acid, and 0.1% to 0.8% alcohol ethoxylate surfactant with deionized water in mass percentage (wt%). The method comprises: performing ultrasonic water washing once to remove surface dust; soaking the washed NdFeB product in the cleaning agent, maintaining the cleaning agent temperature at 24 to 30°C, and reacting for 10 minutes until the welding spots are removed and there are no oxidation pits on the substrate surface; performing ultrasonic water washing twice to remove the cleaning agent on the surface of the product, and then drying the surface moisture of the product to obtain a NdFeB product with a complete and smooth surface after removing the laser welding spots. The present invention eliminates the welding spots on the surface of the laser-cut product by chemical reaction, and uses an acidic cleaning agent to achieve the effect of efficiently removing the laser welding spots, improving the welding spot removal rate, and not damaging the substrate, thereby further improving the product quality.

Description

Technical Field

[0001] The invention relates to the technical field of surface treatment of NdFeB, and in particular to a cleaning agent and a method for removing laser welding spots on the surface of NdFeB. Background Art

[0002] During the NdFeB fiber pulse laser cutting process, the laser beam acts on the upper surface of the substrate to generate thermal stress, causing the substrate at the focus of the laser beam to undergo a phase change from solid to molten state. Due to the action of gravity, the molten state flows out from the lower surface of the substrate. After being blown by the coaxial cooling protective gas, the molten substrate splashes to form sparks. The sparks contact the surface of the substrate and solidify into welding points, such as Figure 1 and Figure 2 shown.

[0003] If solder joints are generated on the surface of the product, it will cause defects such as salt spray defects, missed plating, and surface protrusions at the solder joints after electroplating. Figure 3 As shown, the product will be scrapped, which will seriously affect the quality and production cost of the processed products.

[0004] There are currently two main solutions to the solder joint problem:

[0005] Parameter debugging method: By adjusting the parameters of laser cutting (such as frequency, duty cycle, energy, etc.), the probability of sparks flying to the substrate can be reduced. However, this method still cannot avoid the formation of welds due to sparks flying.

[0006] Chamfering process: Use abrasives to polish and grind the product surface to remove solder joints. However, this method has a low removal rate (<20%), and long-term chamfering may result in poor product appearance, such as knocked edges, corners falling off, and broken pieces. Summary of the invention

[0007] The purpose of the present invention is to provide a cleaning agent and method for removing laser welds on the surface of NdFeB. By chemically eliminating the welds on the surface of laser-cut products and using an acidic cleaning agent, the laser welds can be removed efficiently and quickly without damaging the substrate, thereby further improving product quality.

[0008] To achieve the above object, the solution of the present invention is: a method for removing laser welding spots on the surface of NdFeB, comprising the following steps:

[0009] S1. Solution preparation: 20%-25% nitric acid, 15%-20% hydrofluoric acid and 0.1%-0.8% alcohol ethoxylate surfactant are mixed with deionized water according to mass percentage (wt%) to obtain a cleaning agent;

[0010] S2. One-time water washing: ultrasonically wash the NdFeB product to be treated for 2-5 minutes until the surface dust is removed and then take it out;

[0011] S3, cleaning agent soaking: pour the cleaning agent prepared in step S1 into the cleaning tank, and then soak the NdFeB product after one water washing in the cleaning agent, keep the cleaning agent temperature at 24-30°C, and react for 8-12 minutes until the solder joints are removed and there are no oxidation pits on the substrate surface;

[0012] S4, secondary water washing: After the cleaning is completed, the NdFeB product is ultrasonically washed for 4-8 minutes to remove the cleaning agent on the surface of the product;

[0013] S5. Air drying: After the second water washing is completed, the NdFeB product is taken out and the surface moisture is dried to obtain the NdFeB product after the laser welding spots are removed.

[0014] Further, in step S2, the NdFeB product to be processed is placed in a drum, and the drum is lowered to the first ultrasonic water washing tank station. The computer control system automatically transmits the water washing process parameters to the station. After the drum enters the station, it starts working and uses ultrasonic water washing to remove dust on the surface of the product. When the process is completed, the drum is taken out.

[0015] Further, in step S3, the drum containing the NdFeB product after one water washing is lowered to the top of the cleaning tank station, and the computer control system automatically transmits the cleaning process parameters to the station. After the drum enters the station and the NdFeB is completely immersed in the cleaning agent, it starts to work. The drum speed is 15±2rpm to remove the welding spots on the surface of the product. After cleaning, the drum is lifted out.

[0016] Further, in step S4, the drum containing the cleaned NdFeB product is lowered above the second ultrasonic water washing tank station, and the computer control system automatically transmits the water washing process parameters to the station. After the drum enters the station, it starts working and uses ultrasonic water washing to remove the cleaning agent on the product surface.

[0017] Further, in step S2, the ultrasonic washing time is 3 minutes;

[0018] In step S4, the ultrasonic washing time is 5 minutes.

[0019] A cleaning agent for removing laser welding spots on the surface of NdFeB, wherein the cleaning agent is prepared by mixing 20% ​​to 25% nitric acid, 15% to 20% hydrofluoric acid, 0.1% to 0.8% alcohol ethoxylate surfactant and deionized water in weight percentage (wt%).

[0020] After adopting the above scheme, the beneficial effects of the present invention are:

[0021] First, the present invention utilizes the selective corrosion characteristics of hydrofluoric acid on iron in solder joints, and combines the strong oxidizing property of nitric acid with the protective effect of surfactants to produce an efficient and mild cleaning agent. The cleaning agent can act precisely on solder joints, quickly and effectively remove the main iron components, and improve the solder joint removal rate. The lubrication and protective effects of surfactants can significantly reduce the potential corrosion risk of the substrate, ensuring the integrity and surface finish of the substrate.

[0022] Secondly, the present invention controls key parameters such as the precise ratio of the components in the cleaning agent, the reaction speed, the reaction time and the temperature, thereby ensuring efficient and rapid removal of solder joints while avoiding unnecessary damage to the substrate. Compared with the prior art processing methods such as adjusting laser cutting parameters, polishing and grinding, the overall quality of the product is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an electron microscope image of the weld during NdFeB laser cutting;

[0024] Figure 2 It is a product with defective solder joints in NdFeB laser cutting;

[0025] Figure 3 It is a product with defective solder joints after NdFeB electroplating;

[0026] Figure 4 It is a schematic diagram of the surface of the NdFeB product after the solder joints are removed in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The invention provides a cleaning agent for removing laser welding spots on the surface of NdFeB. The cleaning agent is prepared by mixing 20% ​​to 25% nitric acid, 15% to 20% hydrofluoric acid, 0.1% to 0.8% alcohol ethoxylate surfactant and deionized water in weight percentage (wt%).

[0029] The present invention also provides a method for removing laser welding spots on the surface of NdFeB, comprising the following steps:

[0030] S1. Solution preparation: 20%-25% nitric acid, 15%-20% hydrofluoric acid and 0.1%-0.8% alcohol ethoxylate surfactant are mixed with deionized water according to mass percentage (wt%) to obtain a cleaning agent;

[0031] S2, primary washing: Place the NdFeB product to be processed in the drum, and lower the drum to the first ultrasonic washing tank station. The computer control system automatically transmits the washing process parameters to the station. After the drum enters the station, it starts working and uses ultrasonic washing for 2-5 minutes to remove dust on the product surface. When the process is completed, take out the drum;

[0032] S3, cleaning agent soaking: pour the cleaning agent prepared in step S1 into the cleaning tank, then drop the drum containing the NdFeB product after the first water washing to the top of the cleaning tank station, the computer control system automatically transmits the cleaning process parameters to the station, wait for the drum to enter the station, the NdFeB product is completely immersed in the cleaning agent and then starts working, the drum speed is 15±2rpm, the cleaning agent temperature is controlled at 24~30℃ for 8~12min, until the solder joints are removed and there are no oxidation pits on the substrate surface, after cleaning, the drum is taken out;

[0033] S4, Secondary water washing: The drum containing the cleaned NdFeB products is lowered to the second ultrasonic water washing tank station. The computer control system automatically transmits the water washing process parameters to the station. After the drum enters the station, it starts working and uses ultrasonic water washing for 4~8 minutes to remove the cleaning agent on the product surface.

[0034] S5. Air drying: After the second water washing is completed, the NdFeB product is taken out and the surface moisture is dried using an air curtain to obtain the NdFeB product with the laser welding spots removed.

[0035] In the above method, different proportions of cleaning agents are used to remove laser welding spots on NdFeB products. The composition ratios and cleaning effects of different cleaning agents are shown in Tables 1 and 2:

[0036] Table 1 Cleaning agent composition ratio and cleaning effect

[0037]

[0038] Table 2 Cleaning agent composition ratio and cleaning effect

[0039]

[0040] As shown in Table 1, the cleaning agents of Examples 1 to 7 are excellent in removing solder joints on the surface of NdFeB products. After about 10 minutes of reaction, the solder joint removal rate reaches 85% to 98%, and the substrate surface has no oxidation pits and is basically smooth. The surface conditions of the NdFeB products before and after cleaning are as follows: Figure 2 and Figure 4 shown.

[0041] The main components of the solder joints of NdFeB products are: Fe: 83.27%, O: 11.54%, Nd: 1.33%, C: 3.84%; the thickness of the solder joints is 0.003~0.005mm. Hydrofluoric acid (HF) is introduced to the main components of the solder joints because hydrofluoric acid is a strong acid. Under certain conditions, hydrofluoric acid can react with iron to generate ferrous fluoride and hydrogen. The reaction equation is:

[0042] Fe+2HF = FeF2+H2

[0043] This means that in a hydrofluoric acid environment, iron can react directly with hydrofluoric acid.

[0044] On the other hand, neodymium (Nd) is a rare earth element that reacts differently to iron in hydrofluoric acid. Neodymium forms a protective trifluoride (NdF3) in hydrofluoric acid, which reduces the direct reaction of neodymium with hydrofluoric acid and protects it from further corrosion.

[0045] It can be seen that during the hydrofluoric acid treatment of solder joints, hydrofluoric acid continuously corrodes iron, but neodymium reacts with hydrofluoric acid to form a fluoride protective film, which hinders the further removal of the solder joints. Therefore, a specific solvent is needed to decompose the protective film to continue to remove the solder joints. Therefore, nitric acid is introduced. Nitric acid can continuously oxidize the protective film to achieve the purpose of continuously removing the solder joints.

[0046] The introduction of nitric acid will make the reaction rate too fast, and while removing the solder joints, it will corrode the substrate, forming oxidation pits on the substrate surface, thus affecting the product quality. Further, adding alcohol ethoxylates (Alcohol Ethoxylates) surfactants can effectively reduce the corrosion rate of nitric acid on the substrate, and at the same time has the function of improving the permeability and surface wetting of the acidic cleaning solution, so that the acidic cleaning solution can achieve the effect of removing laser solder joints without damaging the substrate.

[0047] As shown in Table 2, there is only hydrofluoric acid in the solution of Comparative Examples 1 and 2. During the process of treating the solder joints with hydrofluoric acid, the hydrofluoric acid continuously corrodes the iron, but the neodymium reacts with the hydrofluoric acid to form a fluoride protective film, which hinders further cleaning of the solder joints. Therefore, the solder joints cannot be cleaned after reacting for 10 minutes. If the reaction continues, the substrate gradually becomes loose and finally gradually turns into powder, becoming a defective product.

[0048] In Comparative Examples 3 and 4, the solutions contained only nitric acid and hydrofluoric acid without an activator. The solder joints were removed after the reaction lasted for about 3 minutes. However, due to the strong corrosiveness and the fast reaction rate, the substrate was corroded while the solder joints were removed, causing oxidation pits to form on the surface of the substrate, affecting product quality.

[0049] In Comparative Example 5, the concentrations of nitric acid and hydrofluoric acid in the solution were too high, and the substrate was severely corroded after about 5 minutes of reaction, and the solder joints were still not cleaned. In Comparative Example 6, the concentrations of nitric acid and hydrofluoric acid in the solution were too low, and the removal rate reached 10% to 15% after about 20 minutes of reaction.

[0050] In Comparative Example 7, the nitric acid concentration in the solution was too high and the hydrofluoric acid concentration was too low, and the substrate was severely corroded after about 10 minutes of reaction; while in Comparative Example 8, the nitric acid concentration in the solution was too low and the hydrofluoric acid concentration was too high, and both the solder joint and the substrate were corroded after about 30 minutes of reaction, and corrosion pits were generated on the surface of the substrate.

[0051] Compared with Example 7, the concentration of the active agent in the solution of Comparative Example 9 is too high, and the solder joint and the substrate are corroded after 15 minutes of reaction, and corrosion pits are generated in the substrate; compared with Example 7, the reaction temperature of Comparative Example 10 is too low and the reaction time is too long, and the solder joint and the substrate are corroded after 20 minutes, and corrosion pits are generated in the substrate; compared with Example 7, the reaction temperature of Comparative Example 11 is too high, and corrosion pits are generated in the substrate after 5 minutes of reaction.

[0052] Compared with the prior art, the present invention can effectively protect rare earth elements (not limited to neodymium) from excessive corrosion during the chemical reaction process. This treatment method improves the efficiency and stability of solder joint removal and compatibility with different rare earth elements and magnetic material grades. Regardless of the specific type of rare earth elements or the grade of magnetic materials, the present invention can maintain its efficient and stable removal effect, thereby avoiding fluctuations in treatment effects caused by material differences.

[0053] In addition, the cleaning agent formula of the present invention has wide applicability and can be flexibly applied to NdFeB materials of various specifications, sizes and shapes without the need for cumbersome parameter adjustments or equipment modifications for different materials.

[0054] To further illustrate the various embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, a person of ordinary skill in the art should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0055] The above description is only a preferred embodiment of the present invention and is not a limitation on the design of this case. Any equivalent changes made based on the design key of this case shall fall within the protection scope of this case.

Claims

1. A method for removing laser welding spots on the surface of NdFeB, characterized in that: The following steps are involved: S1. Solution preparation: 22% to 25% nitric acid, 18% to 20% hydrofluoric acid and 0.1% to 0.8% alcohol ethoxylate surfactant are mixed with deionized water according to mass percentage (wt%) to obtain a cleaning agent; S2. One-time water washing: ultrasonically wash the NdFeB product to be treated for 2-5 minutes until the surface dust is removed and then take it out; S3, cleaning agent soaking: pour the cleaning agent prepared in step S1 into the cleaning tank, and then soak the NdFeB product after one water washing in the cleaning agent, keep the cleaning agent temperature at 24-30°C, and react for 8-12 minutes until the solder joints are removed and there are no oxidation pits on the substrate surface; S4, secondary water washing: After the cleaning is completed, the NdFeB product is ultrasonically washed for 4-8 minutes to remove the cleaning agent on the surface of the product; S5. Air drying: After the second water washing is completed, the NdFeB product is taken out and the surface moisture is dried to obtain the NdFeB product after the laser welding spots are removed.

2. A method for removing laser weld spots on the surface of NdFeB as claimed in claim 1, characterized in that: In step S2: the NdFeB product to be processed is placed in the drum, and the drum is lowered to the first ultrasonic water washing tank station. The computer control system automatically transmits the water washing process parameters to the station. After the drum enters the station, it starts working and uses ultrasonic water washing to remove dust on the surface of the product. When the process is completed, the drum is taken out.

3. A method for removing laser weld spots on the surface of NdFeB as claimed in claim 2, characterized in that: In step S3, the drum containing the NdFeB product after one water washing is lowered to the top of the cleaning tank station, and the computer control system automatically transmits the cleaning process parameters to the station. After the drum enters the station and the NdFeB product is completely immersed in the cleaning agent, it starts to work. The drum speed is 15±2rpm to remove the welding spots on the surface of the product. After cleaning, the drum is lifted out.

4. A method for removing laser welding spots on the surface of NdFeB as claimed in claim 3, characterized in that: In step S4, the drum containing the cleaned NdFeB product is lowered above the second ultrasonic water washing tank station, and the computer control system automatically transmits the water washing process parameters to the station. After the drum enters the station, it starts working and uses ultrasonic water washing to remove the cleaning agent on the product surface.

5. A method for removing laser weld spots on the surface of NdFeB as claimed in claim 1, characterized in that: In step S2, the ultrasonic washing time is 3 minutes; In step S4, the ultrasonic washing time is 5 minutes.

6. Application of a cleaning agent in removing laser welding spots on the surface of NdFeB, characterized in that: The cleaning agent is prepared by mixing 22% to 25% nitric acid, 18% to 20% hydrofluoric acid, 0.1% to 0.8% alcohol ethoxylate surfactant and deionized water in terms of mass percentage (wt%).

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