A treatment method for increasing the dyne value of the surface nickel coating of NdFeB magnetic steel

Abstract

The invention discloses a treatment method for improving the dyne value of the surface of the nickel-plated layer of NdFeB magnets. A polishing material containing any one of silicon carbide, aluminum oxide and silicon dioxide or a combination of multiple components is used as an abrasive, and nickel-plated steel balls are used as accompanying materials to perform polishing treatment on the NdFeB magnets with the nickel-plated layer. The sharp edges and corners of the abrasive particles "carve" a large number of microscopic scratches on the surface of the nickel-nickel layer of the NdFeB magnets, and then the NdFeB magnets are cleaned multiple times. The method has the advantages of greatly improving the dyne value of the surface of the nickel-plated layer of the NdFeB magnets, and the dyne value is resistant to attenuation during storage and circulation, and the surface dyne value is basically unchanged for 15 days, so that the surface of the NdFeB magnets has good glue wettability at the customer's assembly end, thereby ensuring the reliability of the subsequent assembly and gluing quality.

Description

Technical Field

[0001] The invention relates to a surface treatment method for a nickel-plated layer of a neodymium iron boron magnetic steel, in particular to a treatment method for improving the dyne value of the nickel-plated layer of a neodymium iron boron magnetic steel. Background Art

[0002] NdFeB magnets are widely used in many fields such as consumer electronics, energy-saving motors, smart home appliances, and new energy vehicles due to their mature production process and superior magnetic properties. Because NdFeB materials are relatively active, in order to prevent NdFeB magnets from being corroded, a protective layer must be applied during actual application. Among all kinds of protective coatings, nickel coatings are the most widely used coatings. Common types of nickel plating include: bright nickel, matte nickel, chemical nickel, etc. Due to the characteristics of the nickel plating process, the plating solution contains organic additives. In the process of forming the coating, the organic additives will participate in the reaction and be mixed in the nickel coating. Affected by the organic matter in the organic additives, the dyne value of the nickel coating surface is generally low, and its dyne value is generally below 38#. In addition, during the storage of NdFeB magnets, the organic additives in the nickel coating will gradually precipitate. As the storage time goes by, the dyne value of the nickel coating surface will further decrease. Usually, the dyne value is significantly reduced after 48 hours of storage. This is the fundamental reason why NdFeB magnets are not durable. It is a general consensus in the industry that the initial dyne value of nickel plating is generally low and not durable.

[0003] During the assembly process, NdFeB magnets are usually fixed by gluing. Due to the low dyne value of the nickel plating on the surface of NdFeB magnets, it is difficult to ensure the wettability of glue and the reliability of gluing.

[0004] There are two main methods commonly used in the industry to improve the wettability of glue and the reliability of bonding during the assembly of NdFeB magnets: The first method is cleaning, which usually uses organic cleaning agents such as ethanol or alkaline cleaning liquid to clean the nickel plating on the surface of NdFeB magnets. The advantages of this cleaning method are simple, easy and low cost, but the disadvantages are that it is not durable after cleaning, and the dyne value is significantly reduced after 48 hours of storage, and the dyne increase is low, and the dyne value after cleaning usually does not exceed 40#. The second method is to use a wetting agent to treat the nickel plating on the surface of NdFeB magnets. The advantages of this method are simple and easy, but the disadvantages are that it is not durable after cleaning, and the dyne value is significantly reduced after 48 hours of storage, and the overall dyne increase is still low. The dyne value after treatment usually does not exceed 44#, and the price of wetting agents is relatively high.

[0005] The overall improvement of dyne value by the above two treatment methods is still relatively low, and neither of them can be stored for a long time. Generally, NdFeB magnets require more than 7 days of storage and circulation time from the packaging and shipment end to the customer assembly end. Both of the above two treatment methods are difficult to meet the current storage and assembly needs of NdFeB magnets. Therefore, the industry is currently in urgent need of a treatment method that can greatly improve the dyne value of the surface of the nickel plating layer of NdFeB magnets and resist the attenuation of the dyne value during the storage and circulation process, so as to ensure good glue wettability on the surface of NdFeB magnets and provide guarantee for the reliability of the gluing quality at the subsequent assembly end. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a treatment method for improving the dyne value of the surface nickel plating layer of NdFeB magnets. The treatment method is efficient and low-cost, and can not only greatly improve the dyne value of the surface nickel plating layer of NdFeB magnets, but also resist attenuation of the dyne value during storage and circulation, and the surface dyne value remains basically unchanged for 15 days, so that the surface of the NdFeB magnets has good glue wettability when assembled by the customer, ensuring the reliability of the subsequent assembly and gluing quality.

[0007] The technical solution adopted by the present invention to solve the above technical problems is: a treatment method for improving the dyne value of the surface nickel plating layer of NdFeB magnetic steel, comprising the following steps:

[0008] (1) Polishing treatment: firstly, add abrasive and accompanying materials into a spiral vibration polishing machine, drive the spiral vibration polishing machine to run for 5 minutes to 10 minutes, then add NdFeB magnets with a nickel-plated layer into the spiral vibration polishing machine, and drive the spiral vibration polishing machine to run for 2 hours to 5 hours; the abrasive is a polishing material containing any one of silicon carbide, aluminum oxide, and silicon dioxide or a combination of multiple components, and the accompanying materials are nickel-plated steel balls with a diameter of 1 mm to 3 mm;

[0009] (2) Material sorting: After the polishing process is completed, the mixed material in the spiral vibration polishing machine is taken out and sieved to separate the polished NdFeB magnets, abrasives and accompanying materials. The separated abrasives and accompanying materials can be recycled;

[0010] (3) Pickling treatment: Put the polished NdFeB magnet into the pickling tank and use the pickling solution for cleaning. The pickling solution is dilute sulfuric acid with a solute mass fraction of 2% to 4%. The cleaning time is 30 seconds to 60 seconds. During the cleaning process, turn the NdFeB magnet over to ensure uniform and sufficient cleaning.

[0011] (4) First overflow water washing: The NdFeB magnets washed in step (3) are first washed with overflow water for 5 to 15 seconds;

[0012] (5) Ultrasonic washing: The NdFeB magnets that have been washed with overflow water in step (4) are placed in an ultrasonic washing tank for ultrasonic washing. The water used for ultrasonic washing is industrial pure water. The ultrasonic frequency is 28kHz to 40kHz, and the power per unit area of ​​the bottom of the ultrasonic washing tank is 0.5W / cm 2 ~1W / cm 2 The ultrasonic washing time is 20 seconds to 60 seconds. During the ultrasonic washing process, the NdFeB magnet is turned over to ensure uniform and sufficient cleaning.

[0013] (6) Overflow washing again: the NdFeB magnets that have been ultrasonically washed in step (5) are placed in a water tank for overflow washing again. The water used for overflow washing again is industrial pure water. The washing time is 5 seconds to 30 seconds. During the washing process, the conductivity of the overflow water in the water tank is detected online to control the conductivity of the overflow water to not exceed 20 μs / cm.

[0014] (7) Standing and draining: drain the NdFeB magnet after the overflow water washing in step (6) and hang it for 2 minutes to 5 minutes to allow it to drain naturally;

[0015] (8) Blow-drying treatment: Lay the NdFeB magnet after standing and draining in step (7) on absorbent cotton gauze and perform hot air drying treatment. During the hot air drying process, turn the NdFeB magnet over and wipe the water marks on the surface of the NdFeB magnet with absorbent cotton gauze. Blow hot air until there is no water mark visible. The hot air drying temperature is controlled not to exceed 70°C to avoid water marks formed by local high temperature.

[0016] (9) Drying treatment: The NdFeB magnet dried in step (8) is placed in an oven for drying at a temperature of 50°C to 70°C for 30 minutes to 40 minutes to thoroughly dry the NdFeB magnet.

[0017] In the step (1), the abrasive is 280-320 mesh white corundum; the ratio of the abrasive, the accompanying material, and the NdFeB magnet is 3:1.5:1; the capacity of the spiral vibration polishing machine is 80-150L, ​​and the white corundum is replaced within 3 cycles. In the method, the abrasive, the accompanying material, and the NdFeB magnet are in a specific ratio to avoid the collision of the NdFeB magnet with each other to produce corner chipping, while strengthening the surface polishing pressure of the NdFeB magnet, improving the polishing efficiency and polishing uniformity. In addition, the white corundum has high hardness, sharp microscopic edges and corners, and is not easy to be blunted, and assumes the function of a polishing tool. Therefore, under the combined action of the pressure of the abrasive and the accompanying material mixture and the polishing movement, the sharp edges and corners of the white corundum particles "carve" a large number of microscopic scratches on the surface of the nickel-plated layer of the NdFeB magnet.

[0018] In the step (3), the capacity of the pickling tank is 60-80L, the capacity of the pickling liquid is 30-50L, and air stirring is used during the pickling process. The method can completely dissolve and remove the metal dust particles generated by the polishing treatment on the surface of the NdFeB magnet.

[0019] In the steps (4), (5), (6) and (7), the NdFeB magnets are all placed in nylon mesh bags for processing, and the loading capacity of each nylon mesh bag does not exceed 3 kg.

[0020] Compared with the prior art, the present invention has the advantages of using a polishing material containing any one of silicon carbide, aluminum oxide, and silicon dioxide or a combination of multiple components as an abrasive, using a nickel-plated steel ball with a diameter of 1 mm to 3 mm as a companion material, firstly adding the abrasive and the companion material into a spiral vibration polishing machine, driving the spiral vibration polishing machine to run for 5 minutes to 10 minutes to make the abrasive and the companion material evenly mixed, and then adding a neodymium iron boron magnet with a nickel-plated layer to drive the spiral vibration polishing machine to run for 2 hours to 5 hours. During the operation, under the combined effect of the pressure of the abrasive and the companion material mixture and the polishing motion, the sharp edges and corners of the abrasive particles "carve" a large number of micro scratches on the surface of the nickel-plated layer of the neodymium iron boron magnet. In the dyne value test process, the micro scratches play a rough role. The micro scratches have a capillary effect, so that the dyne liquid diffuses rapidly along the micro scratches, showing a high dyne value. The existence of the scratches does not change with the storage time, so the dyne value is resistant to attenuation, and in the subsequent assembly glue spreading process, the micro scratches also play a capillary role, diffusing the glue to make the glue spreading more uniform, and after the glue is cured, the micro scratches play an anchoring role to enhance the bonding strength. Therefore, the present invention uses less consumables, is low in price, and has a simple and easy processing process, which has the advantage of low cost. It can greatly improve the dyne value of the surface of the nickel-plated layer of the NdFeB magnet, and the dyne value is resistant to attenuation during the storage and circulation process. The surface dyne value is basically unchanged in 15 days, so that the surface of the NdFeB magnet has good glue wettability at the customer's assembly end, thereby ensuring the reliability of the subsequent assembly and gluing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the dyne value test chart of sample 1;

[0022] Figure 2 This is the dyne value test chart of sample 2;

[0023] Figure 3 This is the dyne value test chart of sample 3;

[0024] Figure 4 This is the dyne value test chart of sample 4. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings.

[0026] Embodiment 1: A method for improving the dyne value of the surface of the nickel plating layer of NdFeB magnetic steel, comprising the following steps:

[0027] (1) Polishing treatment: first add the abrasive and the accompanying material into the spiral vibration polishing machine, drive the spiral vibration polishing machine to run for 10 minutes, then add the NdFeB magnet with a nickel-plated layer into the spiral vibration polishing machine, drive the spiral vibration polishing machine to run for 3 hours, and the sharp edges of the abrasive particles "carve" a large number of microscopic scratches on the surface of the nickel-plated layer of the NdFeB magnet; the abrasive is a polishing material containing any one of silicon carbide, aluminum oxide, and silicon dioxide or a combination of multiple components, and the accompanying material is a nickel-plated steel ball with a diameter of 2 mm; wherein the size of the NdFeB magnet with a nickel-plated layer is 6 mm in diameter × 2.3 mm in height, and its nickel-plated layer is formed by a bright nickel electroplating process;

[0028] (2) Material sorting: After the polishing process is completed, the mixed material in the spiral vibration polishing machine is taken out and sieved to separate the polished NdFeB magnets, abrasives and accompanying materials. The separated abrasives and accompanying materials can be recycled;

[0029] (3) Pickling treatment: Put the polished NdFeB magnet into the pickling tank and use the pickling solution to clean it. The pickling solution is dilute sulfuric acid with a solute mass fraction of 3%. The cleaning time is 50 seconds. During the cleaning process, turn the NdFeB magnet over to ensure uniform and sufficient cleaning.

[0030] (4) First overflow water washing: The NdFeB magnets washed in step (3) are first washed with overflow water for 10 seconds;

[0031] (5) Ultrasonic washing: The NdFeB magnets that have been washed with overflow water in step (4) are placed in an ultrasonic washing tank for ultrasonic washing. The water used for ultrasonic washing is industrial pure water. The ultrasonic frequency is 40 kHz and the power per unit area of ​​the bottom of the ultrasonic washing tank is 0.8 W / cm 2 The ultrasonic washing time is 40 seconds. During the ultrasonic washing process, the NdFeB magnet is turned over to ensure uniform and sufficient cleaning.

[0032] (6) Overflow washing again: the NdFeB magnets that have been ultrasonically washed in step (5) are placed in a water tank for overflow washing again. The water used for overflow washing again is industrial pure water. The washing time is 10 seconds. During the washing process, the conductivity of the overflow water in the water tank is detected online. The maximum conductivity of the overflow water is 18 μs / cm.

[0033] (7) Standing and draining: drain the NdFeB magnet after the overflow water washing in step (6) and hang it for 3 minutes to allow it to drain naturally;

[0034] (8) Blow-drying treatment: After standing and draining in step (7), lay the NdFeB magnet on absorbent cotton gauze and perform hot air drying treatment. During the hot air drying process, turn the NdFeB magnet over and wipe the water marks on the surface of the NdFeB magnet with absorbent cotton gauze. Blow-dry with hot air until no water marks are visible. The hot air drying temperature is 62°C.

[0035] (9) Drying treatment: The NdFeB magnet dried in step (8) is placed in an oven for drying at a temperature of 60°C for 40 minutes to thoroughly dry the NdFeB magnet.

[0036] In this embodiment, in step (1), the abrasive is 300 mesh white corundum; the ratio of the abrasive, the accompanying material, and the NdFeB magnetic steel is 3:1.5:1; the capacity of the spiral vibration polishing machine is 100L, and the white corundum is used for the first time.

[0037] In this embodiment, in step (3), the capacity of the pickling tank is 60 L, the capacity of the pickling liquid is 40 L, and air stirring is used to assist in the pickling process.

[0038] In this embodiment, the NdFeB magnets in steps (4), (5), (6) and (7) are all placed in nylon mesh bags for processing, and the loading capacity of each nylon mesh bag is 2 kg.

[0039] Embodiment 2: A method for improving the dyne value of the surface of the nickel plating layer of NdFeB magnetic steel, comprising the following steps:

[0040] (1) Polishing treatment: first, add the abrasive and the accompanying material into the spiral vibration polishing machine, drive the spiral vibration polishing machine to run for 5 minutes, then add the NdFeB magnet with a nickel-plated layer into the spiral vibration polishing machine, drive the spiral vibration polishing machine to run for 4 hours, and the sharp edges of the abrasive particles "carve" a large number of microscopic scratches on the surface of the nickel-plated layer of the NdFeB magnet; the abrasive is a polishing material containing any one of silicon carbide, aluminum oxide, and silicon dioxide or a combination of multiple components, and the accompanying material is a nickel-plated steel ball with a diameter of 2 mm; wherein, the size of the NdFeB magnet with a nickel-plated layer is 6 mm in diameter × 2.3 mm in height, and its nickel-plated layer is formed by electroplating matte nickel process;

[0041] (2) Material sorting: After the polishing process is completed, the mixed material in the spiral vibration polishing machine is taken out and sieved to separate the polished NdFeB magnets, abrasives and accompanying materials. The separated abrasives and accompanying materials can be recycled;

[0042] (3) Pickling treatment: Put the polished NdFeB magnet into the pickling tank and use the pickling solution to clean it. The pickling solution is dilute sulfuric acid with a solute mass fraction of 2%. The cleaning time is 60 seconds. During the cleaning process, turn the NdFeB magnet over to ensure uniform and sufficient cleaning.

[0043] (4) First overflow water washing: The NdFeB magnets washed in step (3) are first washed with overflow water for 10 seconds;

[0044] (5) Ultrasonic washing: The NdFeB magnets that have been washed with overflow water in step (4) are placed in an ultrasonic washing tank for ultrasonic washing. The water used for ultrasonic washing is industrial pure water. The ultrasonic frequency is 40 kHz and the power per unit area of ​​the bottom of the ultrasonic washing tank is 0.8 W / cm 2 The ultrasonic washing time is 60 seconds. During the ultrasonic washing process, the NdFeB magnet is turned over to ensure uniform and sufficient cleaning.

[0045] (6) Overflow washing again: the NdFeB magnets that have been ultrasonically washed in step (5) are placed in a water tank for overflow washing again. The water used for overflow washing again is industrial pure water. The washing time is 10 seconds. During the washing process, the conductivity of the overflow water in the water tank is detected online. The maximum conductivity of the overflow water is 16.5 μs / cm.

[0046] (7) Standing and draining: drain the NdFeB magnet after the overflow water washing in step (6) and hang it for 3 minutes to allow it to drain naturally;

[0047] (8) Blow-drying treatment: After standing and draining in step (7), lay the NdFeB magnet on absorbent cotton gauze and perform hot air drying treatment. During the hot air drying process, turn the NdFeB magnet over and wipe the water marks on the surface of the NdFeB magnet with absorbent cotton gauze. Blow-dry with hot air until there is no water mark visually. The hot air drying temperature is 65°C.

[0048] (9) Drying treatment: The NdFeB magnet dried in step (8) is placed in an oven for drying at a temperature of 50°C for 40 minutes to thoroughly dry the NdFeB magnet.

[0049] In this embodiment, in step (1), the abrasive is 300 mesh white corundum; the ratio of the abrasive, the accompanying material, and the NdFeB magnetic steel is 3:1.5:1; the capacity of the spiral vibration polishing machine is 100L, and the white corundum is used for the second cycle.

[0050] In this embodiment, in step (3), the capacity of the pickling tank is 60 L, the capacity of the pickling liquid is 40 L, and air stirring is used to assist in the pickling process.

[0051] In this embodiment, the NdFeB magnets in steps (4), (5), (6) and (7) are all placed in nylon mesh bags for processing, and the loading capacity of each nylon mesh bag is 2 kg.

[0052] Embodiment 3: A method for improving the dyne value of the surface of the nickel plating layer of NdFeB magnetic steel, comprising the following steps:

[0053] (1) Polishing treatment: first, add the abrasive and the accompanying material into the spiral vibration polishing machine, drive the spiral vibration polishing machine to run for 10 minutes, then add the NdFeB magnet with a nickel-plated layer into the spiral vibration polishing machine, drive the spiral vibration polishing machine to run for 2 hours, and the sharp edges of the abrasive particles "carve" a large number of microscopic scratches on the surface of the nickel-plated layer of the NdFeB magnet; the abrasive is a polishing material containing any one of silicon carbide, aluminum oxide, and silicon dioxide or a combination of multiple components, and the accompanying material is a nickel-plated steel ball with a diameter of 2 mm; wherein, the size of the NdFeB magnet with a nickel-plated layer is 6 mm in diameter × 2.3 mm in height, and its nickel-plated layer is formed by a chemical nickel plating process;

[0054] (2) Material sorting: After the polishing process is completed, the mixed material in the spiral vibration polishing machine is taken out and sieved to separate the polished NdFeB magnets, abrasives and accompanying materials. The separated abrasives and accompanying materials can be recycled;

[0055] (3) Pickling treatment: Place the polished NdFeB magnet into a pickling tank and use a pickling solution to clean it. The pickling solution is dilute sulfuric acid with a solute mass fraction of 4%. The cleaning time is 30 seconds. During the cleaning process, turn the NdFeB magnet over to ensure uniform and sufficient cleaning.

[0056] (4) First overflow water washing: The NdFeB magnets washed in step (3) are first washed with overflow water for 10 seconds;

[0057] (5) Ultrasonic washing: The NdFeB magnets that have been washed with overflow water in step (4) are placed in an ultrasonic washing tank for ultrasonic washing. The water used for ultrasonic washing is industrial pure water. The ultrasonic frequency is 40 kHz and the power per unit area of ​​the bottom of the ultrasonic washing tank is 0.8 W / cm 2 The ultrasonic washing time is 25 seconds. During the ultrasonic washing process, the NdFeB magnet is turned over to ensure uniform and sufficient cleaning.

[0058] (6) Overflow washing again: the NdFeB magnets that have been ultrasonically washed in step (5) are placed in a water tank for overflow washing again. The water used for overflow washing again is industrial pure water. The washing time is 20 seconds. During the washing process, the conductivity of the overflow water in the water tank is detected online. The maximum conductivity of the overflow water is 13 μs / cm.

[0059] (7) Standing and draining: drain the NdFeB magnet after the overflow water washing in step (6) and hang it for 5 minutes to allow it to drain naturally;

[0060] (8) Blow-drying treatment: After standing and draining in step (7), lay the NdFeB magnet on absorbent cotton gauze and perform hot air drying treatment. During the hot air drying process, turn the NdFeB magnet over and wipe the water marks on the surface of the NdFeB magnet with absorbent cotton gauze. Blow-dry with hot air until no water marks are visible. The hot air drying temperature is 68°C.

[0061] (9) Drying treatment: The NdFeB magnet dried in step (8) is placed in an oven for drying at a temperature of 70°C for 30 minutes to thoroughly dry the NdFeB magnet.

[0062] In this embodiment, in step (1), the abrasive is 300 mesh white corundum; the ratio of the abrasive, the accompanying material, and the NdFeB magnetic steel is 3:1.5:1; the capacity of the spiral vibration polishing machine is 100L, and the white corundum is used for the third cycle.

[0063] In this embodiment, in step (3), the capacity of the pickling tank is 60 L, the capacity of the pickling liquid is 40 L, and air stirring is used to assist in the pickling process.

[0064] In this embodiment, the NdFeB magnets in steps (4), (5), (6) and (7) are all placed in nylon mesh bags for processing, and the loading capacity of each nylon mesh bag is 2 kg.

[0065] The following experiment verifies the superiority of the treatment method of the present invention: a NdFeB magnet with a size of 6 mm in diameter and 2.3 mm in height is used and a comparative test is performed after matte nickel electroplating. It should be noted that the commonly used dyne pen numbers are 28# to 72# consecutive double numbers, and the dyne pen number represents the dyne value of the corresponding numerical value; commonly used dyne pen brands include German arcotest, American ACCU, etc., and the German arcotest brand dyne pen is used in the following comparative test; the industry's test method for the dyne value of the surface of NdFeB magnets is: use a dyne pen to draw lines on the surface of NdFeB magnets, and the dyne pen is drawn from low to high numbers in sequence until a certain number of dyne pens shrinks. The maximum dyne value of the tested product is the value of the lower number of the shrinkage number; for example, use three consecutive dyne pens with numbers 52#, 54#, and 56# to draw lines on the surface of NdFeB magnets. There is no shrinkage for 52# and 54#, but shrinkage occurs for 56#. Then the maximum dyne value of the product is 54#. The comparative experiment is as follows;

[0066] Comparative experiment 1: NdFeB magnets that were not treated after matte nickel plating and NdFeB magnets that were treated by the method of the present invention were sampled and tested within 8 hours. Three samples were randomly selected and the highest dyne value was tested. The NdFeB magnet that was not treated after matte nickel plating was called sample 1, and the NdFeB magnet that was treated by the method of the present invention was called sample 2. The dyne value test chart of sample 1 is as follows: Figure 1 As shown; the dyne value test diagram of sample 2 is as follows Figure 2 The test comparison data is shown in Table 1.

[0067] Table 1

[0068]

[0069] Comparative experiment 2: The untreated NdFeB magnet after matte nickel plating and the NdFeB magnet treated by the method of the present invention were exposed to air and stored for 360 hours, and then three samples were randomly selected to test the highest dyne value. The untreated NdFeB magnet after matte nickel plating was called sample 3, and the NdFeB magnet treated by the method of the present invention was called sample 4. The dyne value test chart of sample 3 is as follows: Figure 3 As shown; the dyne value test diagram of sample 4 is as follows Figure 4 The test comparison data is shown in Table 2.

[0070] Table 2

[0071]

[0072] Comparative Test 3: Randomly select 5 samples of each of Samples 1, 2, 3, and 4 described in Comparative Test 1 and Comparative Test 2 for salt spray test, observe and record the results every 24 hours, and stop the test when corrosion phenomena such as spots or red rust appear on the surface of the nickel plating. The test data are shown in Table 3.

[0073] Table 3

[0074]

[0075] Analysis of the test comparison data in Table 1 above shows that the maximum dyne value of the NdFeB magnet plated with matte nickel is 38# before being treated with the method of the present invention; after being treated with the method of the present invention, the maximum dyne value can reach 54#, which is more than 42% higher than before treatment, and the dyne value is greatly improved.

[0076] Analysis of the test comparison data in Table 2 above shows that: for matte nickel-plated NdFeB magnets, when not treated by the method of the present invention, after being exposed to air and stored for 360 hours, its maximum dyne value drops from 38# to 34#; after being treated by the method of the present invention, after being exposed to air and stored for 360 hours, the maximum dyne value remains at 54#, the dyne value does not decay, and the durability advantage is obvious.

[0077] Analysis of the test data in Table 3 shows that there is no significant difference in salt spray corrosion resistance between the samples treated with the method of the present invention and the samples not treated with the method of the present invention. It can be seen that the method of the present invention has no significant effect on the corrosion resistance of the nickel coating.

[0078] In summary, the treatment method for improving the dyne value of the surface of the nickel plating layer of NdFeB magnets of the present invention has a significant effect on improving the dyne value while ensuring the corrosion resistance of the nickel plating layer, and has the advantages of greatly improving the dyne value and being durable, thereby ensuring that the surface of the NdFeB magnets has good glue wettability from the packaging and shipping end to the customer assembly end, providing a guarantee for the reliability of the gluing quality at the subsequent assembly end.

Claims

1. A method for increasing the dyne value of the surface nickel coating of NdFeB magnetic steel, characterized in that The following steps are involved: (1) Polishing treatment: first add the abrasive and the accompanying material into the spiral vibration polishing machine, drive the spiral vibration polishing machine to run for 5 minutes to 10 minutes, then add the NdFeB magnet with a nickel-plated layer into the spiral vibration polishing machine, drive the spiral vibration polishing machine to run for 2 hours to 5 hours, and the sharp edges of the abrasive particles "carve" a large number of microscopic scratches on the surface of the nickel-plated layer of the NdFeB magnet; the abrasive is 280-320 mesh white corundum, the accompanying material is a nickel-plated steel ball with a diameter of 1mm to 3mm, and the ratio of the abrasive, accompanying material, and NdFeB magnet is 3:1.5:1; (2) Material sorting: After the polishing process is completed, the mixed material in the spiral vibration polishing machine is taken out and sieved to separate the polished NdFeB magnets, abrasives and accompanying materials. The separated abrasives and accompanying materials can be recycled; (3) Pickling treatment: Put the polished NdFeB magnet into the pickling tank and use the pickling solution for cleaning. The pickling solution is dilute sulfuric acid with a solute mass fraction of 2% to 4%. The cleaning time is 30 seconds to 60 seconds. During the cleaning process, turn the NdFeB magnet over to ensure uniform and sufficient cleaning. (4) First overflow water washing: The NdFeB magnets washed in step (3) are first washed with overflow water for 5 to 15 seconds; (5) Ultrasonic washing: The NdFeB magnets that have been washed with overflow water in step (4) are placed in an ultrasonic washing tank for ultrasonic washing. The water used for ultrasonic washing is industrial pure water. The ultrasonic frequency is 28kHz to 40kHz, and the power per unit area of ​​the bottom of the ultrasonic washing tank is 0.5W / cm 2 ~1W / cm 2 The ultrasonic washing time is 20 seconds to 60 seconds. During the ultrasonic washing process, the NdFeB magnet is turned over to ensure uniform and sufficient cleaning. (6) Overflow washing again: the NdFeB magnets that have been ultrasonically washed in step (5) are placed in a water tank for overflow washing again. The water used for overflow washing again is industrial pure water. The washing time is 5 seconds to 30 seconds. During the washing process, the conductivity of the overflow water in the water tank is detected online to control the conductivity of the overflow water to not exceed 20 μs / cm. (7) Standing and draining: drain the NdFeB magnet after the overflow water washing in step (6) and hang it for 2 minutes to 5 minutes to allow it to drain naturally; (8) Drying treatment: Lay the NdFeB magnet after standing and draining in step (7) on absorbent cotton gauze and perform hot air drying treatment. During the hot air drying process, turn the NdFeB magnet over and wipe the water marks on the surface of the NdFeB magnet with absorbent cotton gauze. Dry with hot air until there is no water mark visually. The hot air drying temperature is controlled not to exceed 70°C to avoid water marks formed by local high temperature; (9) Drying treatment: The NdFeB magnet dried in step (8) is placed in an oven for drying at a temperature of 50°C to 70°C for 30 minutes to 40 minutes to thoroughly dry the NdFeB magnet.

2. A method for improving the dyne value of the surface nickel plating layer of NdFeB magnetic steel according to claim 1, characterized in that In the step (1), the capacity of the spiral vibration polishing machine is 80 to 150 L, and the white corundum is replaced within 3 cycles.

3. A method for improving the dyne value of the surface nickel plating layer of NdFeB magnetic steel according to claim 1, characterized in that In the step (3), the capacity of the pickling tank is 60 to 80 L, the capacity of the pickling liquid is 30 to 50 L, and air stirring is used to assist in the pickling process.

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