Preparation method of neodymium-iron-boron magnet, neodymium-iron-boron magnet and preparation system

Abstract

The invention discloses a preparation method of a neodymium-iron-boron magnet, the neodymium-iron-boron magnet and a preparation system. The preparation method comprises the steps that a neodymium-iron-boron magnet base body is placed in a first electroplating solution to be subjected to first copper plating treatment, so that a first copper-plated magnet is formed; the first copper-plated magnet is placed in a second electroplating solution to be subjected to second copper plating treatment, so that a second copper-plated magnet is formed; and the second copper-plated magnet is placed in a third electroplating solution to be subjected to nickel-phosphorus electroplating treatment, so that the neodymium-iron-boron magnet comprising multiple electroplated layers is formed. According to the preparation method disclosed by the embodiment of the invention, the batch production requirement can be met in an electroplating manner instead of a chemical plating manner, so that the plating thickness of the neodymium-iron-boron magnets produced in batches can be kept uniform in each batch of production.

Description

Technical Field

[0001] The present disclosure generally relates to the field of electroplating technology. More specifically, the present disclosure relates to a method for preparing a neodymium iron boron magnet, a neodymium iron boron magnet, and a system for preparing a neodymium iron boron magnet. Background Art

[0002] Sintered NdFeB magnets are functional materials widely used in the field of electronic devices. Since the substrate of NdFeB magnets is easily corroded, it is currently protected by electroplating nickel-copper-nickel or copper-nickel coating on the surface of the substrate. As functional devices in the field of electronic devices develop towards high performance and miniaturization, the performance requirements for magnets are getting higher and higher, and the thickness of the coating has become an important factor affecting the performance of magnets. If the coating thickness on the surface of the magnet is relatively thick, it may affect the magnetic properties of the magnet; if the coating thickness on the surface of the magnet is relatively thin, it may affect the corrosion resistance of the magnet.

[0003] At present, chemical plating is often used in the method of forming a coating on the surface of NdFeB magnets, or chemical plating is used in the preparation process of part of the coating in the composite coating, such as chemical nickel-phosphorus coating. However, the thickness of the coating of chemical plating is difficult to control, especially for mass production of magnet products with ultra-thin coatings. It is difficult to control the thickness of each batch of magnets to maintain uniformity and standardization, which will make it difficult for mass-produced magnet products to meet the needs of the consumer electronics field.

[0004] In view of this, there is an urgent need to provide a preparation scheme for NdFeB magnets to meet the requirements of mass production. Summary of the invention

[0005] In order to at least solve one or more of the technical problems mentioned above, the present disclosure provides, in multiple aspects, a method for preparing a NdFeB magnet, a NdFeB magnet, and a system for preparing a NdFeB magnet.

[0006] In the first aspect, the present disclosure proposes a method for preparing a neodymium iron boron magnet, comprising: placing a neodymium iron boron magnet substrate in a first electroplating solution for a first copper plating treatment to form a first copper-plated magnet; placing the first copper-plated magnet in a second electroplating solution for a second copper plating treatment to form a second copper-plated magnet; and placing the second copper-plated magnet in a third electroplating solution for a nickel-phosphorus electroplating treatment to form a neodymium iron boron magnet including multiple electroplating layers.

[0007] In some embodiments, the third electroplating solution includes nickel sulfate, A additive and B additive, wherein the concentration of the nickel sulfate is 270-360 g / L, the volume content of the A additive is 110-150 ml / L, and the volume content of the B additive is 80-120 ml / L; the A additive includes at least one of phosphate, phosphite, hypophosphite, phosphoric acid, and phosphorous acid, and the phosphorus content in the A additive is 10-25 g / L; the B additive includes methanol and sodium citrate, wherein the concentration of sodium citrate in the B additive is 50-100 g / L, and the volume content of the methanol in the B additive is 1-5 ml / L.

[0008] In some embodiments, the A additive includes sodium hypophosphite and phosphoric acid, and the mass ratio of the sodium hypophosphite to the phosphoric acid is 40-60:1.

[0009] In other embodiments, when the nickel-phosphorus electroplating treatment is started, the volume ratio of the A additive to the B additive in the third electroplating solution is 1.5:1.

[0010] In other embodiments, the preparation method further includes: during the nickel-phosphorus electroplating process, adding the A additive and the B additive to the third electroplating solution once or multiple times, and the volume ratio of the A additive to the B additive in each adding operation is 1:2.

[0011] In some further embodiments, the A additive and the B additive are added to the third plating solution in proportion every 20 ampere hours.

[0012] In some embodiments, the control conditions of the nickel-phosphorus electroplating treatment include: controlling the temperature of the third electroplating solution to 47-53° C. and the pH value to 2-2.6.

[0013] In other embodiments, the current density of the nickel-phosphorus electroplating treatment is controlled to be 0.05-0.15 ASD, and the electroplating time is 3-4 hours.

[0014] In some embodiments, placing the second copper-plated magnet in a third electroplating solution for nickel-phosphorus electroplating treatment includes: placing the second copper-plated magnet in the third electroplating solution for a first nickel-phosphorus electroplating treatment to form a neodymium iron boron magnet including a first electroplated nickel-phosphorus layer; and placing the neodymium iron boron magnet including the first electroplated nickel-phosphorus layer in the third electroplating solution for a second nickel-phosphorus electroplating treatment to form a neodymium iron boron magnet including a first electroplated nickel-phosphorus layer and a second electroplated nickel-phosphorus layer.

[0015] In other embodiments, in the first nickel-phosphorus electroplating treatment, the pH value of the third electroplating solution is controlled to be 2.3-2.6; in the second nickel-phosphorus electroplating treatment, the pH value of the third electroplating solution is controlled to be 2.0-2.3.

[0016] In some other embodiments, the current density of the first nickel-phosphorus electroplating treatment is controlled to be 0.10-0.15 ASD, and the current density of the second nickel-phosphorus electroplating treatment is controlled to be 0.05-0.10 ASD.

[0017] In other embodiments, when performing the nickel-phosphorus electroplating treatment, the preparation method further includes: monitoring the nickel concentration in the third electroplating solution; and when the nickel concentration is lower than 60 g / L, adding nickel sulfate to the third electroplating solution so that the nickel concentration in the third electroplating solution is maintained at 60-80 g / L.

[0018] In some other embodiments, the preparation method further includes: setting at least one anode copper plate and at least one first insoluble anode in the first electroplating solution to form a first electrolysis circuit with the NdFeB magnet matrix; setting at least one second insoluble anode and at least one cathode in the first electroplating solution to form a second electrolysis circuit; and during the first copper plating process, controlling the opening and closing of the second electrolysis circuit according to the copper ion concentration in the first electroplating solution.

[0019] In some embodiments, controlling the opening and closing of the second electrolysis circuit according to the copper ion concentration in the first electroplating solution includes: closing the second electrolysis circuit in response to the copper ion concentration in the first electroplating solution being less than 2.2 g / L; and opening the second electrolysis circuit in response to the copper ion concentration in the first electroplating solution being greater than 2.4 g / L.

[0020] In other embodiments, the first electroplating solution includes a copper salt, 80-140 g / L of a complexing agent, and 2-4 ml / L of a wetting agent solution, and the copper ion concentration in the first electroplating solution is 2-3 g / L.

[0021] In some further embodiments, the wetting agent solution comprises a solution of sodium alkyl ether phosphate, and the concentration of the solution of sodium alkyl ether phosphate is 5-10 wt %.

[0022] In some embodiments, the control conditions of the first copper plating treatment include: controlling the temperature of the first electroplating solution to 17-23° C. and the pH value to 9.6-10; and controlling the electroplating time of the first copper plating treatment to 1-2 hours and the current density to 0.05-0.15 ASD.

[0023] In other embodiments, the second electroplating solution includes a copper salt, a complexing agent, a first additive and a second additive, wherein the copper ion concentration in the second electroplating solution is 8.5-9.5 g / L; the concentration of the complexing agent is 110-170 g / L; the first additive includes anhydrous bismuth nitrate in a mass ratio of 1-5wt%, glycine in a mass ratio of 1-5wt% and potassium carbonate in a mass ratio of 1-10wt%; the second additive includes sodium chlorite in a mass ratio of 1-10wt% and sodium sulfate in a mass ratio of 1-10wt%; when the second copper plating treatment is started, the volume ratio of the first additive to the second additive in the second electroplating solution is 1:4, and the volume content of the second additive in the second electroplating solution is 7-9 ml / L.

[0024] In some other embodiments, the preparation method further includes: during the second copper plating process, adding the first additive and the second additive to the second electroplating solution once or multiple times, and the volume ratio of the first additive to the second additive in each adding operation is 1:2.

[0025] In some embodiments, the first additive and the second additive are added to the second plating solution in proportion every 50 ampere hours.

[0026] In other embodiments, the control conditions of the second copper plating treatment include: controlling the temperature of the second electroplating solution to 57-63° C. and the pH value to 9.4-9.8; and controlling the electroplating time of the second copper plating treatment to 3-4 hours and the current density to 0.05-0.15 ASD.

[0027] In some other embodiments, before performing at least one of the first copper plating treatment, the second copper plating treatment and the nickel-phosphorus electroplating treatment, a shock current is applied, the magnitude of the shock current is 1.4-2 times the magnitude of the current during electroplating, the first copper plating treatment or the second copper plating treatment applies the shock current for 10-30 minutes, or the nickel-phosphorus electroplating treatment applies the shock current for 20-50 minutes.

[0028] In a second aspect, the present disclosure provides a neodymium iron boron magnet prepared according to any preparation method described in the first aspect of the present disclosure.

[0029] In a third aspect, the present disclosure provides a neodymium iron boron magnet, comprising: a neodymium iron boron magnet substrate; an electroplated copper layer attached to the surface of the neodymium iron boron magnet substrate, the thickness of the electroplated copper layer being ≤4μm, for example, 2.0μm, 2.5μm, 3.0μm, 3.5μm, 4.0μm, and a thickness tolerance of ±1μm; and an electroplated nickel-phosphorus layer attached to the electroplated copper layer, the thickness of the electroplated nickel-phosphorus layer being ≤3μm, for example, 1.0μm, 1.5μm, 2.0μm, 2.5μm, 3.0μm, and a thickness tolerance of ±1μm.

[0030] In some embodiments, the total thickness of the electroplated copper layer and the electroplated nickel-phosphorus layer is ≤7 μm, for example, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, 5.5 μm, 6.0 μm, 6.5 μm, or 7.0 μm.

[0031] In some embodiments, the phosphorus content of the electroplated nickel-phosphorus layer is ≥ 11 wt %.

[0032] In some other embodiments, the electroplated nickel-phosphorus layer includes a first electroplated nickel-phosphorus layer and a second electroplated nickel-phosphorus layer, and the first electroplated nickel-phosphorus layer has a thickness of 1-2 μm, and the second electroplated nickel-phosphorus layer has a thickness of 0.5-1 μm.

[0033] In some embodiments, the phosphorus content of the first electroplated nickel-phosphorus layer is 9-12 wt %, and the phosphorus content of the second electroplated nickel-phosphorus layer is 12-14 wt %.

[0034] In some other embodiments, the electroplated copper layer includes a bottom copper plating layer and a thick copper plating layer, wherein the bottom copper plating layer is attached to the surface of the NdFeB magnet substrate, the thick copper plating layer is located between the bottom copper plating layer and the electroplated nickel-phosphorus layer, and the thickness of the bottom copper plating layer is 0.8-1.2 μm.

[0035] In some embodiments, the surface glossiness of the NdFeB magnet is 100-200 GU.

[0036] In a fourth aspect, the present disclosure provides a system for preparing a neodymium iron boron magnet, comprising: a first copper plating system for performing a first copper plating treatment on a neodymium iron boron magnet substrate to form a first copper-plated magnet; a second copper plating system for performing a second copper plating treatment on the first copper-plated magnet to form a second copper-plated magnet; and an electroplating nickel-phosphorus system for performing an electroplating nickel-phosphorus treatment on the second copper-plated magnet to form a neodymium iron boron magnet comprising multiple electroplated layers.

[0037] In some embodiments, the nickel-phosphorus electroplating system includes: a third electroplating tank, which contains a third electroplating solution, and the third electroplating solution includes nickel sulfate, A additive and B additive, wherein the concentration of the nickel sulfate is 270-360g / L, the volume content of the A additive is 110-150ml / L, and the volume content of the B additive is 80-120ml / L; the A additive includes at least one of phosphate, phosphite, hypophosphite, phosphoric acid, and phosphorous acid, and the phosphorus content in the A additive is 10-25g / L; the B additive includes methanol and sodium citrate, wherein the concentration of sodium citrate in the B additive is 50-100g / L, and the volume content of the methanol in the B additive is 1-5ml / L; the volume ratio of the A additive to the B additive is 1.5:1.

[0038] In some embodiments, the A additive includes sodium hypophosphite and phosphoric acid, and the mass ratio of the sodium hypophosphite to the phosphoric acid is 40-60:1.

[0039] In other embodiments, the current density in the third electroplating tank is controlled to be 0.05-0.15 ASD, and the electroplating time in the third electroplating tank is controlled to be 3-4 hours.

[0040] In some embodiments, the nickel-phosphorus electroplating treatment includes a first nickel-phosphorus electroplating treatment and a second nickel-phosphorus electroplating treatment, wherein in the first nickel-phosphorus electroplating treatment, the current density in the third electroplating tank is 0.10-0.15ASD; in the second nickel-phosphorus electroplating treatment, the current density in the third electroplating tank is 0.05-0.10ASD.

[0041] In other embodiments, the nickel-phosphorus electroplating system also includes: a third management tank, which is connected to the third electroplating tank; an agent A replenishing device, which is connected to the third management tank and contains the agent A additive; an agent B replenishing device, which is connected to the third management tank and contains the agent B additive; a third control device, which is used to control the agent A replenishing device and the agent B replenishing device to respectively add the agent A and the agent B to the third management tank, and in each replenishing operation, the replenishment volume ratio of the agent A to the agent B is controlled to be 1:2.

[0042] In some further embodiments, the third control device controls the agent A replenishing device and the agent B replenishing device to replenish the additive A and the additive B into the third electroplating solution once every 20 ampere hours.

[0043] In some embodiments, the third control device is further used to: control the temperature of the third electroplating solution in the third management tank to 47-53° C.; and control the pH value of the third electroplating solution in the third management tank to 2-2.6.

[0044] In other embodiments, the nickel-phosphorus electroplating treatment includes a first nickel-phosphorus electroplating treatment and a second nickel-phosphorus electroplating treatment, and the third control device is also used to: in the first nickel-phosphorus electroplating treatment, control the pH value of the third electroplating solution in the third management tank to be 2.3-2.6; in the second nickel-phosphorus electroplating treatment, control the pH value of the third electroplating solution in the third management tank to be 2.0-2.3.

[0045] In other embodiments, the nickel-phosphorus electroplating system also includes: a nickel ion online analysis device, which is connected to the third management tank and used to monitor the nickel concentration of the third electroplating solution in the third management tank; and a nickel replenishing device, which is connected to the third management tank and contains a nickel sulfate solution; the third control device is also used to control the nickel replenishing device to replenish the nickel sulfate solution into the third management tank when the nickel concentration in the third electroplating solution is lower than 60g / L, so that the nickel concentration in the third electroplating solution is maintained at 60-80g / L.

[0046] In some other embodiments, the first copper plating system includes: a first electroplating tank, which contains a first electroplating solution, the first electroplating solution includes a copper salt, 80-140 g / L of a complexing agent and 2-4 ml / L of a wetting agent solution, and the copper ion concentration in the first electroplating solution is 2-3 g / L.

[0047] In some embodiments, the wetting agent solution includes a solution of sodium alkyl ether phosphate, and the concentration of the solution of sodium alkyl ether phosphate is 5-10 wt %.

[0048] In other embodiments, at least one anode copper plate and at least one first insoluble anode are provided in the first electroplating tank to form a first electrolytic circuit with the NdFeB magnet substrate; the first copper plating system also includes: a first control device, used to: control the current density in the first electrolytic circuit to 0.05-0.15ASD; control the electroplating time of the first electrolytic circuit to 3-4 hours.

[0049] In some embodiments, the first copper plating system also includes: a first management tank, which is connected to the first electroplating tank and is provided with at least one second insoluble anode and at least one cathode to form a second electrolysis circuit; and a copper ion analysis device, which is connected to the first management tank and is used to detect the copper ion concentration in the first electroplating solution in the first management tank; and the first control device is also used to control the opening and closing of the second electrolysis circuit according to the copper ion concentration in the first electroplating solution.

[0050] In other embodiments, the first control device is further used to: in response to the copper ion concentration in the first electroplating solution being less than 2.2 g / L, close the second electrolysis circuit; in response to the copper ion concentration in the first electroplating solution being greater than 2.4 g / L, open the second electrolysis circuit.

[0051] In some further embodiments, the first control device is further used to: control the temperature of the first electroplating solution in the first management tank to be 17-23° C.; and control the pH value of the first electroplating solution in the first management tank to be 9.6-10.

[0052] In some embodiments, the second copper plating system includes: a second electroplating tank, which contains a second electroplating solution, the second electroplating solution includes a copper salt, a complexing agent, a first additive and a second additive, wherein the copper ion concentration in the second electroplating solution is 8.5-9.5g / L; the concentration of the complexing agent is 110-170g / L; the first additive includes anhydrous bismuth nitrate, 1-5wt% glycine and 1-10wt% potassium carbonate in a mass ratio of 1-5wt%; the second additive includes sodium chlorite and 1-10wt% sodium sulfate in a mass ratio of 1-10wt%; the volume ratio of the first additive to the second additive is 1:4, and the volume content of the second additive in the second electroplating solution is 7-9ml / L.

[0053] In other embodiments, the second copper plating system also includes: a second management tank, which is connected to the second electroplating tank; a first liquid replenishing device, which is connected to the second management tank and contains the first additive; a second liquid replenishing device, which is connected to the second management tank and contains the second additive; a second control device, which is used to control the first liquid replenishing device and the second liquid replenishing device to add the first additive and the second additive to the second management tank respectively, and in each replenishing operation, the replenishment volume ratio of the first additive to the second additive is controlled to be 1:2.

[0054] In some further embodiments, the second control device controls the first liquid replenishing device and the second liquid replenishing device to replenish the first additive and the second additive into the second electroplating solution once every 50 ampere hours.

[0055] In some embodiments, the second control device is also used to: control the temperature of the second electroplating solution in the second management tank to 57-63°C; control the pH value of the second electroplating solution in the second management tank to 9.4-9.8; and control the electroplating time of the second electroplating tank to 3-4 hours and the current density to 0.05-0.15ASD.

[0056] Through the scheme for preparing NdFeB magnets as provided above, the disclosed embodiment can meet the mass production requirements by electroplating rather than chemical plating by sequentially subjecting the NdFeB magnets to a first copper plating treatment, a second copper plating treatment and an electroplating nickel-phosphorus treatment, so that the coating thickness of the mass-produced NdFeB magnets can be kept uniform in each batch of production, thereby avoiding the problem of large differences in coating thickness between magnet monomers. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] By reading the detailed description below with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood. In the accompanying drawings, several embodiments of the present disclosure are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0058] Figure 1 A flow chart of a method for preparing a NdFeB magnet according to an embodiment of the present disclosure is shown;

[0059] Figure 2 A schematic block diagram of a system for preparing a neodymium iron boron magnet according to an embodiment of the present disclosure is shown;

[0060] Figure 3 shows a schematic diagram of a first copper plating system according to an embodiment of the present disclosure;

[0061] Figure 4 shows a schematic diagram of a second copper plating system according to an embodiment of the present disclosure;

[0062] Figure 5 A schematic diagram of a second copper plating system including a recovery tank according to an embodiment of the present disclosure is shown;

[0063] Figure 6 shows a schematic diagram of a nickel phosphorus electroplating system according to an embodiment of the present disclosure;

[0064] Figure 7 An electron microscope image of any magnet product sample prepared in Example 3 of the present disclosure is shown. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0066] It should be understood that the terms "include" and "comprising" used in the specification and claims of the present disclosure indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0067] It should also be understood that the terms used in this disclosure are only for the purpose of describing specific embodiments and are not intended to limit the disclosure. As used in this disclosure and claims, the singular forms of "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It should also be further understood that the term "and / or" used in this disclosure and claims refers to any combination of one or more of the associated listed items and all possible combinations, including these combinations.

[0068] The specific implementation of the present disclosure is described in detail below with reference to the accompanying drawings.

[0069] Figure 1 FIG. 1 shows a flow chart of a method for preparing a NdFeB magnet according to an embodiment of the present disclosure. Figure 1 As shown in , the preparation method 100 may include: in step 102, the NdFeB magnet substrate may be placed in a first electroplating solution for a first copper plating treatment to form a first copper-plated magnet. In some embodiments, the first electroplating solution may include a copper salt, 80-140 g / L of a complexing agent, and 2-4 ml / L of a wetting agent solution, wherein the copper ion concentration in the first electroplating solution may be 2-3 g / L.

[0070] In some embodiments, the NdFeB magnet matrix is ​​a sintered NdFeB magnet matrix. The NdFeB magnet matrix can be a material obtained by machining and surface cleaning of NdFeB raw materials. In other embodiments, the copper salt in the first electroplating solution can include at least one of basic copper carbonate, copper sulfate, etc. In some embodiments, the complexing agent can include HEDP (i.e., "hydroxyethyl diphosphonic acid") and the like. The complexing agent can be used to combine with copper ions to reduce the content of free copper ions in the first electroplating solution, thereby stabilizing the plating solution, promoting normal dissolution of the anode, and inhibiting the replacement reaction on the surface of the NdFeB magnet, thereby forming a bottom copper plating layer with better bonding force on the surface of the NdFeB magnet. In some other embodiments, the wetting agent solution can include, for example, a solution of sodium salt of alkyl ether phosphate, and the concentration of the solution of sodium salt of alkyl ether phosphate can be 5-10wt% (wt% represents mass percentage). By adding sodium alkyl ether phosphate, the pores in the bottom copper coating formed on the surface of the NdFeB magnet during the first copper plating process are eliminated, so that the density of the bottom copper coating is better, thereby effectively avoiding the occurrence of replacement reaction during the second copper plating process.

[0071] In some embodiments, the control conditions of the first copper plating treatment may include: controlling the temperature of the first electroplating solution to 17-23°C and the pH value to 9.6-10; and controlling the electroplating time of the first copper plating treatment to 1-2 hours and the current density to 0.05-0.15ASD. The pH value of the first electroplating solution can be controlled by adding a pH regulator to the first electroplating solution, wherein the pH regulator may include KOH, or NaOH, etc. Since the potential of copper is higher than that of NdFeB magnets, copper ions tend to replace iron when they contact the surface of NdFeB magnets. If a replacement reaction occurs, the replacement copper layer formed on the surface of NdFeB magnets has a lower interface bonding force with the surface of NdFeB magnets. Therefore, it is necessary to minimize or avoid the formation of a replacement copper layer on the surface of NdFeB magnets. By controlling the temperature of the first electroplating solution within the lower temperature range of 17-23°C during the first copper plating treatment, it is beneficial to suppress the occurrence of the replacement reaction, thereby reducing the formation of a replacement copper layer on the surface of NdFeB magnets. By controlling the electroplating time and current density, the thickness of the bottom copper plating layer can be controlled.

[0072] In other embodiments, when performing the first copper plating treatment, controlling the temperature of the first electroplating solution to 17-23° C. may include: cooling the first electroplating solution to keep the temperature of the first electroplating solution at 17-23° C. during the first copper plating treatment. For example, a cooling device such as a cooling coil may be provided in the first electroplating solution, or a cooling device may be coated on the outside of the first electroplating device, etc., to achieve the purpose of controlling the temperature of the first electroplating solution.

[0073] In some other embodiments, the first copper plating treatment may further include: detecting the concentration change of the complexing agent in the first electroplating solution to determine the amount and time of adding the complexing agent to the first electroplating solution, wherein the addition time may be calculated in ampere hours; and adding the complexing agent to the first electroplating solution according to the amount and time of addition. Since the complexing agent is consumed during the electroplating process, maintaining the stability of the concentration of the complexing agent in the first electroplating solution will help ensure the stability of the electroplating process. In some embodiments, the concentration change of the complexing agent in the first electroplating solution may be detected in the initial stage of the first copper plating treatment, and the concentration of the complexing agent in the first electroplating solution may be stabilized between 80 and 140 g / L by adding the complexing agent to the first electroplating solution, and the amount and time of adding the complexing agent to stabilize the concentration of the complexing agent may be determined based on the process. In other embodiments, the determined addition time may be 20 ampere hours, and the complexing agent may be added to the first electroplating solution once every 20 ampere hours.

[0074] In some embodiments, step 102 may further include: setting at least one anode copper plate and at least one first insoluble anode in the first electroplating solution to form a first electrolysis circuit with the NdFeB magnet matrix; setting at least one second insoluble anode and at least one cathode in the first electroplating solution to form a second electrolysis circuit; and during the first copper plating process, controlling the opening and closing of the second electrolysis circuit according to the copper ion concentration in the first electroplating solution.

[0075] The soluble anode and the first insoluble anode can be provided independently or integrally. In some embodiments, the soluble anode can include a copper anode; the first insoluble anode can include a graphite anode and / or a stainless steel anode, etc. In other embodiments, the first copper plating treatment can be performed in a first electroplating tank, the first electroplating tank can contain a first electroplating solution, the NdFeB magnet substrate is placed in the first electroplating solution, and the soluble anode and the first insoluble anode can be placed in the first electroplating tank, so that the NdFeB magnet substrate in the first electroplating tank is used as a cathode to form a first electrolysis circuit for electroplating reaction.

[0076] As the soluble anode dissolves, the copper ion concentration in the first electroplating solution will increase. By setting the first insoluble anode, the copper ions dissolved by the anode can be reduced, and the increase in the copper ion concentration in the electroplating solution can be suppressed. In other words, the setting of the first insoluble anode can consume the copper ions in the first electroplating solution to compensate for the copper ion concentration deviation caused by the increase in copper ion concentration caused by the dissolution reaction of the soluble anode, thereby playing a role in controlling the stability of the copper ion concentration in the first electroplating solution.

[0077] In some embodiments, the second insoluble anode may include a graphite anode and / or a stainless steel anode. The cathode in the second electrolysis loop may be made of other materials other than the NdFeB magnet itself, which is not limited herein. The second electrolysis loop and the first electrolysis loop are two independent electrolysis loops and are independently controlled.

[0078] In some application scenarios, the first electrolysis circuit and the second electrolysis circuit can be simultaneously arranged in the first electroplating tank. In other application scenarios, the first electrolysis circuit can be arranged in the first electroplating tank, and the second electrolysis circuit can be arranged in the first management tank to facilitate the control of the second electrolysis circuit, wherein the first management tank can be connected to the first electroplating tank, so that the first electroplating solution can circulate in the first electroplating tank and the first management tank.

[0079] During the first copper plating process, the copper ion concentration in the first electroplating solution can be detected so as to control the opening and closing of the second electrolytic circuit according to the change of the copper ion concentration. For example, in some embodiments, according to the copper ion concentration in the first electroplating solution, controlling the opening and closing of the second electrolytic circuit includes: in response to the copper ion concentration in the first electroplating solution being less than 2.2g / L, closing the second electrolytic circuit; in response to the copper ion concentration in the first electroplating solution being greater than 2.4g / L, opening the second electrolytic circuit. Opening and closing the second electrolytic circuit can be achieved by controlling the power supply in the second electrolytic circuit, or by controlling the switching device on the second electrolytic circuit.

[0080] By controlling the opening and closing of the second electrolysis circuit according to the copper ion concentration, the copper ion concentration in the first electrolyte can be controlled more accurately, and since the second electrolysis circuit is independent of the first electrolysis circuit, the opening and closing of the second electrolysis circuit will not affect the electrochemical reaction in the first electrolysis circuit. By setting up the second electrolysis circuit, on the basis of setting up the first insoluble anode to control the copper ion concentration, the copper ion concentration in the first electrolyte can be further fine-tuned and accurately controlled, so that the copper ion concentration in the first electrolyte can be maintained within a small fluctuation range of 2-3g / L.

[0081] In some embodiments, according to the first copper plating process of the disclosed embodiment, the thickness of the bottom copper plating layer formed can be 0.8-1.2 μm. In a preferred embodiment, the thickness of the bottom copper plating layer can be 1 μm. By making the thickness of the bottom copper plating layer reach 1 μm, the porosity of the bottom copper plating layer can be significantly reduced while forming an ultra-thin copper layer, achieving a better priming effect, which is beneficial to the subsequent second copper plating process.

[0082] like Figure 1As shown in , after obtaining the first copper-plated magnet, the process can proceed to step 104, and the first copper-plated magnet can be placed in a second electroplating solution for a second copper plating treatment to form a second copper-plated magnet. In some embodiments, the second electroplating solution may include a copper salt, a complexing agent, a first additive, and a second additive, wherein the copper ion concentration in the second electroplating solution may be 8.5-9.5 g / L; the concentration of the complexing agent may be 110-170 g / L; the first additive may include anhydrous bismuth nitrate with a mass ratio of 1-5wt%, glycine with a mass ratio of 1-5wt%, and potassium carbonate with a mass ratio of 1-10wt%; the second additive may include sodium chlorite with a mass ratio of 1-10wt% and sodium sulfate with a mass ratio of 1-10wt%; when the second copper plating treatment is started, the volume ratio of the first additive to the second additive in the second electroplating solution may be 1:4, and the volume content of the second additive in the second electroplating solution may be 7-9ml / L.

[0083] In some embodiments, the complexing agent may include HEDP and the like. The first additive may play a role in brightening, and the second additive may play a role in making the brightness of the coating uniform. Under the coordinated action of the first additive and the second additive, the surface of the thick copper coating formed after the second copper plating treatment may have lower porosity, higher density, suitable glossiness, and fine crystals, which is not only conducive to making the surface of the NdFeB magnet product finally formed smoother and brighter, but also conducive to improving the corrosion resistance of the NdFeB magnet product. In addition, according to the first additive and the second additive used in combination in the embodiment of the present disclosure, it is possible to make it unnecessary to use a weak acid for activation in the second copper plating treatment, which can effectively avoid the corrosion damage of the bottom copper coating on the surface of the first copper-plated magnet that has been formed by using a weak acid, thereby ensuring the copper plating effect of the second copper plating treatment and being conducive to the corrosion resistance of the product.

[0084] In some embodiments, the first copper plating process and / or the second copper plating process may adopt a barrel plating process. As the second copper plating process proceeds, the concentrations of the first additive and the second additive in the second electroplating solution change due to electroplating consumption and consumption of the plating solution brought out by the roller in the barrel plating process. In order to stabilize the concentrations of the first additive and the second additive in the second electroplating solution so that the final NdFeB magnet product has high-quality and stable plating properties, the first additive and the second additive may be added during the second copper plating process.

[0085] In some other embodiments, step 104 may further include: during the second copper plating process, adding the first additive and the second additive to the second electroplating solution once or more, and the volume ratio of the first additive to the second additive in each adding operation may be 1:2. Since the consumption of the first additive and the second additive is different during the electroplating process, the volume ratio of the first additive to the second additive in the adding operation is set to 1:2, which is different from the volume ratio when the cylinder is opened (when the second copper plating process is started), and the concentration of the first additive and the second additive in the second copper plating process can be effectively ensured to remain stable. In a preferred embodiment, the first additive and the second additive can be added to the second electroplating solution in proportion every 50 ampere hours.

[0086] In other embodiments, the control conditions of the second copper plating treatment may include: controlling the temperature of the second electroplating solution to 57-63°C and the pH value to 9.4-9.8; and controlling the electroplating time of the second copper plating treatment to 3-4 hours and the current density to 0.05-0.15ASD. Controlling the pH value of the second electroplating solution can be achieved by adding a pH regulator to the second electroplating solution, wherein the pH regulator may include KOH, or NaOH, etc. Controlling the temperature of the second electroplating solution within a higher temperature range is conducive to increasing the electroplating speed. By controlling the electroplating time and current density, it is beneficial to control the thickness of the thick copper plating layer.

[0087] Since the second copper plating treatment is electroplating the first copper plating magnet, the bottom copper plating layer on the first copper plating magnet can form a good protective effect on the surface of the NdFeB magnet substrate, so that no replacement reaction occurs during the second copper plating treatment. Therefore, the cathode current efficiency during the second copper plating treatment is higher, and the copper consumption of electroplating and the copper ions dissolved by the soluble anode can form a balance, so that an insoluble anode does not need to be set in the electrolysis circuit formed by the first copper plating magnet and the soluble anode. However, the inventors found that due to the high temperature of electroplating during the second copper plating treatment, the water in the second electroplating solution may evaporate, which may affect the copper ion concentration in the second electroplating solution, and further affect the uniformity of the coating thickness of a single second copper plating magnet.

[0088] Based on this, in some other embodiments, step 104 may also include: in the second copper plating process, automatically replenishing the second electroplating solution to control the difference between the highest liquid level height and the lowest liquid level height of the second electroplating solution within a preset range, so that the fluctuation range of the copper ion concentration difference in the second electroplating solution is less than 2%. The fluctuation range of the copper ion concentration difference here is less than 2%, which means that during the second copper plating process, the copper ion concentration of the second electroplating solution may fluctuate, and the difference between the maximum concentration and the minimum concentration of copper ions during the fluctuation process can be less than 2%, so that the stability of the copper ion concentration can be ensured, which is conducive to ensuring the uniformity of the coating thickness of the second copper-plated magnet. In this embodiment, the liquid level of the second electroplating solution is controlled by automatic replenishment, so that the fluctuation range of the copper ion concentration in the second electroplating solution can be less than 2%, thereby achieving the control of the copper ion concentration in the second electroplating solution to be kept within the range of 8.5-9.5g / L. The smaller the fluctuation range of the copper ion concentration difference, the more conducive to ensuring the stability of the copper ion concentration and the uniformity of the coating thickness. In some preferred embodiments, the fluctuation range of the copper ion concentration difference can be controlled to be below 1.7%.

[0089] In some embodiments, a second electroplating tank can be provided for accommodating a second electroplating solution, and for accommodating a first copper-plated magnet and a soluble anode, so as to perform a second copper plating treatment on the first copper-plated magnet; a second management tank connected to the second electroplating device can also be provided, and the second management tank can be used to control and manage the second electroplating solution, for example, to control and manage the concentration of copper ions in the second electroplating solution. In some preferred embodiments, assuming that the volume of the second electroplating tank is 3000L and the volume of the second management tank is 500L, the difference between the highest liquid level and the lowest liquid level in the second management tank can be controlled within 50L (i.e., a preset range). This embodiment is only exemplary, and the preset range can be determined according to the actual production conditions such as the actual volume of the container used, other devices arranged in the container, etc., as long as the fluctuation range of the copper ion concentration difference can be controlled to be less than 2%.

[0090] In other embodiments, the second copper plating treatment can adopt a roller plating process, and a second electroplating tank can be set to contain the second electroplating liquid to perform the second copper plating treatment on the first copper-plated magnet; at least one recovery tank can be set after the second electroplating tank to clean the drum; according to the liquid level of the second electroplating liquid, the liquid in at least one recovery tank can be controlled to be transported to the second electroplating tank to replenish the liquid level of the second electroplating liquid, thereby realizing automatic liquid replenishment to the second electroplating liquid.

[0091] By controlling the copper ion concentration in the first electroplating solution to remain within a small range of 2-3 g / L during the first copper plating process, and by controlling the copper ion concentration in the second electroplating solution to remain within a small range of 8.5-9.5 g / L during the second copper plating process, a stable electroplating speed can be controlled, and the electroplating speed will not fluctuate, thereby ensuring the uniformity of the thickness of the electroplated copper layer of a single magnet, so that the thickness tolerance of the electroplated copper layer can be within a small range of ±1 μm, achieving a higher plating accuracy.

[0092] like Figure 1 As further shown in FIG. 1 , in step 106, the second copper-plated magnet may be placed in a third electroplating solution for nickel-phosphorus electroplating treatment to form a neodymium iron boron magnet including multiple electroplated layers. The multiple electroplated layers may include an electroplated copper layer and an electroplated nickel-phosphorus layer, wherein the electroplated copper layer may include a bottom copper plating layer and a thick copper plating layer. The electroplated nickel-phosphorus layer may include a single electroplated nickel-phosphorus layer or multiple electroplated nickel-phosphorus layers. For example, in some embodiments, the electroplated nickel-phosphorus layer may include a first electroplated nickel-phosphorus layer and a second electroplated nickel-phosphorus layer, wherein the first electroplated nickel-phosphorus layer may be attached to the electroplated copper layer, and the second electroplated nickel-phosphorus layer may be attached to the first electroplated nickel-phosphorus layer. The two layers of electroplated nickel-phosphorus layers may be achieved by performing two nickel-phosphorus electroplating treatments on the second copper-plated magnet. In some embodiments, a third electroplating solution having the same composition and concentration may be used during the two nickel-phosphorus electroplating treatments. In other embodiments, the first electroplated nickel-phosphorus layer and the second electroplated nickel-phosphorus layer formed may be well combined so as to be integrated.

[0093] In some embodiments, the third electroplating solution may include nickel sulfate, additive A and additive B, wherein the concentration of nickel sulfate may be 270-360 g / L, the volume content of additive A may be 110-150 ml / L, and the volume content of additive B may be 80-120 ml / L; additive A may include at least one of phosphate, phosphite, hypophosphite, phosphoric acid, and phosphorous acid, and the phosphorus content in additive A may be 10-25 g / L; additive B may include methanol and sodium citrate, wherein the concentration of sodium citrate in additive B may be 50-100 g / L, and the volume content of methanol in additive B may be 1-5 ml / L; at the beginning of the nickel-phosphorus electroplating treatment, the volume ratio of additive A to additive B in the third electroplating solution may be 1.5:1. The nickel ion content in the third electroplating solution may be 60-80 g / L. In other embodiments, additive A may include sodium hypophosphite and phosphoric acid, and the mass ratio of sodium hypophosphite to phosphoric acid may be 40-60:1.

[0094] Nickel sulfate provides nickel ions, and additive A provides phosphorus ions. Sodium citrate acts as a complexing agent, and the content of sodium citrate in the third electroplating solution affects the phosphorus content. If the content of sodium citrate is too little, the phosphorus content will be low. However, sodium citrate is an easily decomposed substance, and it is easy to self-decompose at high temperatures, and too low temperatures affect the reaction rate. Therefore, in some embodiments, the control conditions for electroplating nickel-phosphorus treatment may include: controlling the temperature of the third electroplating solution to 47-53°C (e.g., 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C), and the pH value to 2-2.6 (e.g., 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6). Controlling the temperature of the third electroplating solution at around 50°C is conducive to preventing sodium citrate from self-decomposing, while ensuring the reaction rate of the electroplating reaction. The pH value can be controlled by controlling the amount of phosphoric acid added, or other acidic pH regulators can be added.

[0095] In some embodiments, the above-mentioned nickel-phosphorus electroplating treatment may include multiple nickel-phosphorus electroplating treatment processes to form a multi-layer nickel-phosphorus electroplating layer. For example, in some embodiments, step 106 may include: placing the second copper-plated magnet in a third electroplating solution for a first nickel-phosphorus electroplating treatment to form a neodymium iron boron magnet including a first nickel-phosphorus electroplating layer; and placing the neodymium iron boron magnet including the first nickel-phosphorus electroplating layer in a third electroplating solution for a second nickel-phosphorus electroplating treatment to form a neodymium iron boron magnet including the first nickel-phosphorus electroplating layer and the second nickel-phosphorus electroplating layer.

[0096] In some embodiments, in the first nickel-phosphorus electroplating treatment, the pH value of the third electroplating solution can be controlled to be 2.3-2.6 (e.g., 2.3, 2.4, 2.5, 2.6); in the second nickel-phosphorus electroplating treatment, the pH value of the third electroplating solution can be controlled to be 2.0-2.3 (e.g., 2.0, 2.1, 2.2, 2.3). In other embodiments, the current density of the first nickel-phosphorus electroplating treatment can be controlled to be 0.10-0.15ASD (e.g., 0.10ASD, 0.11ASD, 0.12ASD, 0.13ASD, 0.14ASD, 0.15ASD), and the current density of the second nickel-phosphorus electroplating treatment can be controlled to be 0.05-0.10ASD (e.g., 0.05ASD, 0.06ASD, 0.07ASD, 0.08ASD, 0.09ASD, 0.10ASD).

[0097] By using a relatively large current density in the first nickel-phosphorus electroplating treatment, it is helpful to increase the electroplating speed. By using a relatively small pH value and current density in the second nickel-phosphorus electroplating treatment, it is helpful to obtain a second nickel-phosphorus electroplating layer with a smaller thickness and a higher phosphorus content. According to such a setting, not only the total thickness of the two layers of nickel-phosphorus electroplating layers can still be ≤3μm, thereby not increasing the thickness of the electroplated layer of the NdFeB magnet, but also it is helpful to further increase the phosphorus content of the nickel-phosphorus electroplating layer, so as to further improve the corrosion resistance of the NdFeB magnet.

[0098] In addition, it can be understood that other process conditions of each nickel-phosphorus electroplating treatment in multiple nickel-phosphorus electroplating treatments, such as the temperature of the third plating solution, the addition of additives, nickel concentration monitoring, the application of impact current, etc., can be the same as the corresponding process conditions of the nickel-phosphorus electroplating treatment described above or below, and will not be repeated.

[0099] The inventors have found that in order to obtain an electroplated nickel-phosphorus layer with uniform thickness and high phosphorus content to improve the appearance quality and corrosion resistance of the magnet product, the key factor is to control the ratio between the nickel content and the phosphorus content during the electroplating nickel-phosphorus treatment process and maintain the stability of the two contents. Based on this, the inventors further optimized the preparation method of the disclosed embodiment.

[0100] In some embodiments, step 106 may further include: during the nickel-phosphorus electroplating process, adding additive A and additive B to the third electroplating solution once or multiple times to ensure that the phosphorus content in the third electroplating solution is stably maintained within the desired concentration range, wherein the volume ratio of additive A to additive B in each addition operation may be 1:2. Additive A and additive B may be pre-configured separately, and added separately at each addition, and the volume ratio of additive A to additive B is 1:2. Due to the different consumption rates of additive A and additive B during the nickel-phosphorus electroplating process, the inventor creatively discovered that when the volume ratio of additive A to additive B is 1.5:1 at the beginning of the nickel-phosphorus electroplating process, the volume ratio of additive A to additive B is 1:2 at each addition, which can ensure the actual ratio between additive A and additive B in the third electroplating solution during the electroplating process and is conducive to maintaining a stable phosphorus content. In some other embodiments, the A additive and the B additive may be added to the third electroplating solution in proportion every 20 ampere hours to ensure that the phosphorus content in the third electroplating solution does not fluctuate.

[0101] In other embodiments, when performing the nickel-phosphorus electroplating treatment, step 106 may further include: monitoring the nickel concentration in the third electroplating solution; and when the nickel concentration is lower than 60 g / L, adding nickel sulfate to the third electroplating solution, so that the nickel concentration in the third electroplating solution is maintained at 60-80 g / L. By monitoring the nickel concentration in the third electroplating solution and timely adding the nickel source, it is beneficial to maintain the stability of the nickel ion concentration in the third electroplating solution.

[0102] In some other embodiments, before performing at least one of the first copper plating treatment, the second copper plating treatment and the nickel-phosphorus electroplating treatment, a shock current can be applied. The magnitude of the shock current can be 1.4-2 times the magnitude of the current during electroplating. The time for applying the shock current for the first copper plating treatment or the second copper plating treatment is 10-30 minutes, or the time for applying the shock current for the nickel-phosphorus electroplating treatment is 20-50 minutes.

[0103] In some embodiments, before the first copper plating treatment, the NdFeB magnet substrate can be placed in the first electroplating solution and a surge current can be applied. The magnitude of the surge current can be set to 1.4-2 times the magnitude of the electroplating current during the first copper plating treatment, and the time for applying the surge current can be 10-30 minutes. In other embodiments, before the second copper plating treatment, the first copper-plated magnet can be placed in the second electroplating solution and a surge current can be applied. The magnitude of the surge current can be set to 1.4-2 times the magnitude of the electroplating current during the second copper plating treatment, and the time for applying the surge current can be 10-30 minutes. In some other embodiments, before the nickel-phosphorus electroplating treatment, the second copper-plated magnet can be placed in the third electroplating solution and a surge current can be applied. The magnitude of the surge current can be set to 1.4-2 times the magnitude of the electroplating current during the nickel-phosphorus electroplating treatment, and the time for applying the surge current for the first copper plating treatment or the second copper plating treatment is 10-30 minutes, or the time for applying the surge current for the nickel-phosphorus electroplating treatment is 20-50 minutes.

[0104] By applying a surge current before at least one of the first copper plating treatment, the second copper plating treatment and the nickel-phosphorus electroplating treatment, the electroplating speed can be increased in a short time, so that at least one of the surfaces of the NdFeB magnet substrate, the first copper plating magnet and the second copper plating magnet can be quickly electroplated with a pre-plating layer as protection, which can effectively reduce the risk of corrosion to the NdFeB magnet during the electroplating process. After applying the surge current, normal electroplating operations are performed and the appropriate electroplating speed is controlled, so that the desired coating structure can be formed more accurately while avoiding the risk of corrosion.

[0105] Combination of the above Figure 1An exemplary description is given of the preparation method of the NdFeB magnet according to the embodiment of the present disclosure. It can be understood that the produced NdFeB magnet has an electroplated nickel-phosphorus layer through the nickel-phosphorus electroplating treatment. Compared with the chemical nickel-phosphorus plating layer, the electroplating process is more convenient for standardized control, which is beneficial to control the uniformity of the thickness of the electroplated layer of the NdFeB magnet, thereby enabling mass production of magnet products with balanced quality.

[0106] It can also be understood that the above description is exemplary and not restrictive. For example, the preparation method 100 may not be limited to only including the steps 102, 104 and 106 shown in the figure. In other embodiments, the preparation method 100 may also include before step 102: immersing the NdFeB magnet substrate in a pretreatment solution for pretreatment, and placing the pretreated NdFeB magnet substrate in a first electroplating solution for a first copper plating treatment, wherein the pretreatment solution may include a complexing agent and a pH regulator, the concentration of the complexing agent may be 80-140 g / L, and the pH regulator is used to adjust the pH value of the pretreatment solution to 9.6-10. In some embodiments, the pH regulator may include potassium hydroxide or sodium hydroxide, etc. In other embodiments, the complexing agent may include HEDP, etc. The concentration and pH value of the complexing agent in the pretreatment solution may be the same as the concentration and pH value of the complexing agent in the first electroplating solution, so that when the pretreated NdFeB magnet substrate is subjected to the first copper plating treatment, it will not affect the first electroplating solution.

[0107] Furthermore, since the pretreatment liquid acts directly on the NdFeB magnet substrate, compared with setting the pretreatment liquid as an acidic solution or a neutral solution, setting the pretreatment liquid as an alkaline solution (i.e., the pH value is set to 9.6-10) is conducive to avoiding the corrosion of the NdFeB magnet substrate by the acidic solution or the neutral solution, and avoiding oxidation on the surface of the NdFeB magnet substrate. The corrosion and oxidation of the surface of the NdFeB magnet substrate will be detrimental to the bonding force between the coating and the substrate, and will also affect the magnetic properties of the magnet product. In addition, the pretreated NdFeB magnet substrate will undergo a first copper plating treatment. If the pretreatment liquid on the surface of the NdFeB magnet substrate is acidic or neutral, the acidic or neutral solution is continuously introduced into the first electroplating solution, which will cause the pH value of the first electroplating solution to continue to decrease, which is not conducive to the stability of the process parameters in the first copper plating treatment.

[0108] Before the first copper plating treatment is performed, the surface of the NdFeB magnet substrate is first pretreated as described above, so that the surface of the NdFeB magnet substrate is placed in the first electroplating solution surrounded by a chelating agent, which can effectively prevent the free copper ions in the first electroplating solution from undergoing a replacement reaction on the surface of the NdFeB magnet substrate, thereby facilitating the electrochemical reaction of the copper ions combined with the chelating agent in the first electroplating solution to form a bottom copper plating layer, thereby improving the bonding strength of the plating layer on the surface of the NdFeB magnet substrate.

[0109] Further, according to Figure 1 The NdFeB magnet prepared by the preparation method 100 shown may include a NdFeB magnet substrate and a multi-layer electroplating layer, wherein the multi-layer electroplating layer includes an electroplated copper layer and an electroplated nickel-phosphorus layer, the electroplated copper layer is attached to the surface of the NdFeB magnet substrate, and the electroplated nickel-phosphorus layer is attached to the electroplated copper layer. By controlling the process conditions in the first copper plating treatment and the second copper plating treatment, the thickness of the electroplated copper layer can be made ≤4μm, such as 2μm, 2.5μm, 3μm, 3.5μm, 4μm, etc. In particular, the control of the copper ion concentration during the first copper plating treatment and the second copper plating treatment makes the thickness tolerance of the electroplated copper layer only ±1μm.

[0110] The thickness of the obtained electroplated nickel-phosphorus layer is ≤3 μm, such as 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm. In other embodiments, the electroplated nickel-phosphorus layer may include a first electroplated nickel-phosphorus layer and a second electroplated nickel-phosphorus layer, and the thickness of the first electroplated nickel-phosphorus layer may be 1-2 μm, such as 1 μm, 1.25 μm, 1.5 μm, 1.75 μm, 2 μm, etc.; the thickness of the second electroplated nickel-phosphorus layer may be 0.5-1 μm, such as 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm. In particular, by controlling the nickel content and phosphorus content stability during the nickel-phosphorus electroplating process, the thickness tolerance of the nickel-phosphorus electroplating layer is only ±1 μm, and the phosphorus content of the nickel-phosphorus electroplating layer can reach ≥9wt%, or even ≥11wt% (e.g., 11wt%, 11.5wt%, 12wt%, 12.5wt%, 13wt%, 13.5wt%, 14wt%, etc.). In some embodiments, the phosphorus content of the nickel-phosphorus electroplating layer is 9-14wt%. The phosphorus content of the nickel-phosphorus electroplating layer here refers to the phosphorus content on the surface of the nickel-phosphorus electroplating layer of the product.

[0111] Furthermore, in some other embodiments, the electroplated nickel-phosphorus layer may include a first electroplated nickel-phosphorus layer and a second electroplated nickel-phosphorus layer, and the phosphorus content of the first electroplated nickel-phosphorus layer may be 9-12wt%, for example, 9wt%, 9.5wt%, 10wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt%, etc.; the phosphorus content of the second electroplated nickel-phosphorus layer may reach 12-14wt%, for example, 12wt%, 12.5wt%, 13wt%, 13.5wt%, 14wt%, etc.

[0112] In other embodiments, the total thickness of the electroplated copper layer and the electroplated nickel phosphorus layer may be ≤7 μm, for example, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, etc.

[0113] In some other embodiments, the electroplated copper layer may include a bottom copper plating layer and a thick copper plating layer, wherein the bottom copper plating layer is attached to the surface of the NdFeB magnet substrate, and the thick copper plating layer is located between the bottom copper plating layer and the electroplated nickel-phosphorus layer. After the first copper plating treatment, the thickness of the bottom copper plating layer is 0.8-1.2 μm, such as 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, etc. On this basis, through the second copper plating treatment, a thick copper plating layer with uniform thickness can be quickly covered on the surface of the bottom copper plating layer, and pores or unevenness that may exist on the bottom copper plating layer can be filled to improve the corrosion resistance and other properties of the NdFeB magnet.

[0114] In some embodiments, by using the first additive and the second additive in the second copper plating process, it is helpful to improve the density and glossiness of the NdFeB magnet coating, so that the glossiness of the NdFeB magnet can reach 100-200GU, such as 100GU, 105GU, 110GU, 115GU, 120GU, 125GU, 130GU, 135GU, 140GU, ​​145GU, 150GU, 155GU, 160GU, 165GU, 170GU, 175GU, 180GU, 185GU, 190GU, 195GU, 200GU. The glossiness in this range can not only make the surface of the NdFeB magnet bright and smooth, but also make the magnet product easier to be identified by optical detection equipment in the subsequent automatic assembly process for easy grasping, thereby better meeting the needs of the consumer electronic product field. In comparison, if the gloss is too low or too high, there is a risk that the optical inspection equipment cannot identify it.

[0115] Figure 2 A schematic block diagram of a system for preparing a neodymium iron boron magnet according to an embodiment of the present disclosure is shown. Figure 2 As shown in the figure, the system 200 may include: a first copper plating system 210, used to perform a first copper plating treatment on the NdFeB magnet substrate to form a first copper plating magnet; a second copper plating system 220, used to perform a second copper plating treatment on the first copper plating magnet to form a second copper plating magnet; and a nickel-phosphorus electroplating system 230, used to perform a nickel-phosphorus electroplating treatment on the second copper plating magnet to form a NdFeB magnet including multiple electroplating layers.

[0116] In some embodiments, the first copper plating system 210 may include one or more electroplating devices for implementing the first copper plating process. In other embodiments, the first copper plating system 210 may include a roller plating device or a rack plating device for performing the first copper plating process on the NdFeB magnet substrate using a roller plating process or a rack plating process.

[0117] In other embodiments, the second copper plating system 220 may include one or more electroplating devices for implementing the second copper plating process. In some embodiments, the second copper plating system 220 may include a roller plating device or a rack plating device for performing the second copper plating process on the first copper-plated magnet using a roller plating process or a rack plating process.

[0118] In some other embodiments, the nickel-phosphorus electroplating system 230 may include one or more electroplating devices for implementing the nickel-phosphorus electroplating process. In some embodiments, the nickel-phosphorus electroplating system 230 may include a barrel plating device or a rack plating device for performing the nickel-phosphorus electroplating process on the second copper-plated magnet using a barrel plating process or a rack plating process. In some embodiments, the nickel-phosphorus electroplating system 230 may be used for one or more nickel-phosphorus electroplating processes.

[0119] The above description is exemplary and not restrictive, and the present disclosure further optimizes the technical solution in multiple implementations to achieve better technical effects. In order to further understand the system of the implementation of the present disclosure, an exemplary description will be given below in conjunction with more drawings.

[0120] Figure 3 A schematic diagram of a first copper plating system according to an embodiment of the present disclosure is shown. As can be seen from the following description, Figure 3 The first copper plating system shown can be used to implement the above Figure 2 An exemplary embodiment of the first copper plating system is shown, but is not intended to limit the first copper plating system of the disclosed embodiment, and will be described in detail below.

[0121] like Figure 3 As shown in the figure, the first copper plating system 210 may include a first electroplating tank 301, and the first electroplating tank 301 may contain a first electroplating solution, and the first electroplating solution may include a copper salt, 80-140 g / L of a complexing agent, and 2-4 ml / L of a wetting agent solution, and the copper ion concentration in the first electroplating solution is 2-3 g / L. In some embodiments, the wetting agent solution may include a solution of a sodium salt of an alkyl ether phosphate, and the concentration of the sodium salt of the alkyl ether phosphate is 5-10 wt%. The first electroplating solution is described in the above text. Figure 1 It has been described in detail and will not be repeated here.

[0122] In some embodiments, the first electroplating tank 301 may be a barrel plating tank or a rack plating tank. In other embodiments, the volume of the first electroplating tank 301 may be set to, for example, 3000 L. In still other embodiments, a filter may be provided at the open end of the first electroplating tank 301, and the filter may be used to filter the air entering the first electroplating tank 301 to remove impurities in the air entering the first electroplating tank 301.

[0123] In some embodiments, at least one anode copper plate 307 and at least one first insoluble anode 308 may be provided in the first electroplating tank 301, and the at least one anode copper plate 307 and the at least one first insoluble anode 308 may form a first electrolytic circuit with the NdFeB magnet substrate 10. The first electrolytic circuit may also include circuit components such as a power supply and a rectifier. The first copper plating system 210 may also include: a first control device 303, which may be used to: control the current density in the first electrolytic circuit (such as shown by the dotted line in the figure) to 0.05-0.15ASD; control the electroplating time of the first electrolytic circuit to 3-4 hours.

[0124] The first control device 303 can be implemented in the form of software and / or hardware. For example, in some embodiments, the first control device 303 may include a processor, a controller, etc. In other embodiments, the first control device 303 may be configured with, for example, a PLC (programmable logic controller) program, etc. In some application scenarios, parameters such as the current density in the first electrolysis loop and the electroplating time of the first electrolysis loop may be pre-set in the first control device 303, so that the automatic control of the first copper plating system 210 can be achieved. In some other embodiments, the first copper plating system 210 may also include a human-computer interaction interface, which may be directly arranged on the first control device 303, or connected to the first control device 303, so as to display control data and / or facilitate the user to configure the first control device 303.

[0125] like Figure 3 As further shown in the figure, in some embodiments, the first copper plating system 210 may also include: a first management tank 302, which is connected to the first electroplating tank 301, and at least one second insoluble anode 309 and at least one cathode 310 may be provided inside the first management tank 302 to form a second electrolysis circuit (for example, as shown by the dotted line in the figure). The second electrolysis circuit may also include circuit components such as a power supply and a rectifier. The second electrolysis circuit may be independently provided with the first electrolysis circuit, and the first control device 303 may independently control the first electrolysis circuit and the second electrolysis circuit.

[0126] In some embodiments, the volume of the first management tank 302 may be smaller than the volume of the first electroplating tank 301. In other embodiments, the volume of the first management tank 302 may be, for example, 500L. In yet other embodiments, the first management tank 302 may be arranged at a position lower than the first electroplating tank 301, and the first electroplating solution in the first electroplating tank 301 may be transported to the first management tank 302 through a downpipe (e.g., the pipeline where the arrow in the figure is located), and the first electroplating solution in the first management tank 302 may be transported back to the first electroplating tank 301 through a reflux pipeline connecting the first management tank 302 and the first electroplating tank 301 (e.g., the path indicated by the arrow pointing from the first management tank 302 to the first electroplating tank 301 in the figure), and the reflux pipeline may be provided with a power device such as a circulating pump to drive the flow of the first electroplating solution. Based on this, the communication between the first management tank 302 and the first electroplating tank 301 can be achieved.

[0127] In other embodiments, the first copper plating system 210 may further include a copper ion analysis device 305, which may be connected to the first management tank 302 for detecting the copper ion concentration in the first electroplating solution in the first management tank 302; and the first control device 303 may also be used to control the opening and closing of the second electrolysis circuit according to the copper ion concentration in the first electroplating solution.

[0128] In some embodiments, the copper ion analysis device 305 may include a copper ion online analysis device. In other embodiments, before using the copper ion analysis device 305 to detect the first electrolyte in the first management tank 302, deionized water (or DI water) and a standard solution with a known copper ion concentration can be taken respectively, wherein the deionized water can be used as a reference for a copper ion concentration of zero, and the copper ion analysis device 305 is used to detect the deionized water and the standard solution of each known copper ion concentration (for example, the detection probe of the copper ion analysis device 305 is inserted into each liquid for measurement), and the absorption intensity of each liquid to the fixed light source is recorded; then the corresponding relationship between the concentration of copper ions and the absorption intensity to the fixed light source can be determined, and based on this, for example, a working curve can be made, and the corresponding relationship and / or the working curve can be written into the first control device 303.

[0129] Based on such a setting, when the copper ion analysis device 305 is used to detect the first electrolyte in the first management tank 302, the absorption intensity of the copper ions in the first electroplating solution to the fixed light source can be continuously detected online. After receiving the absorption intensity detected by the copper ion analysis device 305, the first control device 303 can reversely calculate the copper ion concentration in the first electroplating solution according to the pre-stored corresponding relationship. In other embodiments, the above-mentioned corresponding relationship and / or working curve can also be stored in the copper ion analysis device 305, and used to determine the copper ion concentration according to the detected absorption intensity.

[0130] In some application scenarios, the first control device 303 can also be configured as: in response to the copper ion concentration obtained by reverse calculation being within the corresponding relationship and / or the working curve range, the copper ion analysis device 305 can be controlled to continuously monitor; in response to the copper ion concentration obtained by reverse calculation being not within the corresponding relationship and / or the working curve range, it is judged that the copper ion concentration in the first electroplating tank 301 may be abnormal, and an alarm signal can be issued to request manual inspection or manual intervention.

[0131] In other embodiments, the first control device 303 may be further configured to: in response to the copper ion concentration in the first electroplating solution being less than the first preset threshold, close the second electrolysis circuit; in response to the copper ion concentration in the first electroplating solution being greater than the second preset threshold, open the second electrolysis circuit, wherein the second preset threshold is greater than the first preset threshold. The first preset threshold and the second preset threshold may be determined according to the stable concentration range required for the copper ion concentration in the first electroplating solution. According to such a setting, the concentration of copper ions in the first electroplating solution may be automatically controlled and fine-tuned so that the copper ion concentration in the first electroplating solution can be stabilized within the desired concentration range. In some embodiments, the first preset threshold may be 2.2 g / L, and the second preset threshold may be 2.4 g / L, so that the copper ion concentration in the first electroplating solution may be controlled to be stabilized within the range of 2-3 g / L.

[0132] In some other embodiments, the first control device 303 can also be used to: control the temperature of the first electroplating solution in the first management tank 302 to be 17-23°C; control the pH value of the first electroplating solution in the first management tank 302 to be 9.6-10. Since the temperature of the first electroplating solution is controlled to be relatively low, a cooling device 304 can be provided in the first management tank 302. In some embodiments, the cooling device 304 can be a cooling coil, and cooling water can be passed into the cooling coil to achieve the purpose of cooling. In other embodiments, a temperature detection device (such as a temperature probe or a temperature sensor, etc.) for detecting the temperature of the first electroplating solution can be respectively provided in the first electroplating tank 301 and the first management tank 302, and the temperature detection device can be connected to the first control device 303, and the first control device 303 can control the cooling temperature of the cooling device 304 according to the temperature detected by the temperature detection device.

[0133] The pH value of the first electroplating solution in the first management tank 302 can be controlled by adding a pH regulator to the first management tank 302. In some embodiments, the first copper plating system 210 may further include, for example, a supplementing device 306 as shown in the figure, in which a pH regulator may be contained, so that under the control of the first control device 303, the pH regulator may be added to the first management tank 302 in a timely and / or quantitative manner. In other embodiments, the supplementing device 306 may not be limited to one, and may be provided in multiples as required, for example, a supplementing device for supplementing a complexing agent may be provided, so that during the first copper plating process, a complexing agent may be supplemented to the first management tank 302 under the control of the first control device 303.

[0134] Combination of the above Figure 3 The first copper plating system according to the embodiment of the present disclosure is described exemplarily. It is to be understood that the above description is exemplified and not restrictive. For example, in some embodiments, the first copper plating system 210 may also include a pretreatment tank, which may contain a solution including a complexing agent and is used to attach the complexing agent to the NdFeB magnet substrate in the pretreatment tank before the NdFeB magnet substrate enters the first electroplating tank 301 for copper plating. Other embodiments that can be obtained by those skilled in the art without creative labor under the guidance of the embodiments of the present disclosure are also within the scope of protection of the present disclosure.

[0135] Figure 4 A schematic diagram of a second copper plating system according to an embodiment of the present disclosure is shown. As can be seen from the following description, Figure 4 The second copper plating system shown can be used to implement the above Figure 2 An exemplary embodiment of the second copper plating system shown, but not limiting of the second copper plating system of the disclosed embodiment, will be described in detail below.

[0136] like Figure 4 As shown in, the second copper plating system 220 may include: a second electroplating tank 401, which may contain a second electroplating solution, the second electroplating solution may include a copper salt, a complexing agent, a first additive and a second additive, wherein the copper ion concentration in the second electroplating solution is 8.5-9.5g / L; the concentration of the complexing agent is 110-170g / L; the first additive includes anhydrous bismuth nitrate, 1-5wt% glycine and 1-10wt% potassium carbonate in a mass ratio of 1-5wt%; the second additive includes sodium chlorite and 1-10wt% sodium sulfate in a mass ratio of 1-10wt%; the volume ratio of the first additive to the second additive is 1:4, and the volume content of the second additive in the second electroplating solution is 7-9ml / L.

[0137] The second plating solution is combined with Figure 1Detailed description has been given here, which will not be repeated here. In some embodiments, the second electroplating tank 401 can be a barrel plating tank or a rack plating tank. In other embodiments, the volume of the second electroplating tank 401 can be set to, for example, 3000L. In some other embodiments, a filter can be provided at the open end of the second electroplating tank 401, and the filter can be used to filter the air entering the second electroplating tank 401 to remove impurities in the air entering the second electroplating tank 401.

[0138] In some embodiments, at least one soluble anode 405 may be provided in the second electroplating tank 401, and the at least one soluble anode 405 may form an electrolytic circuit with the first copper-plating magnet 20. The electrolytic circuit may also include circuit components such as a power supply and a rectifier. The second copper-plating system 220 may also include: a second control device 403, which may be used to: control the current density in the second electroplating tank 401 to be 0.05-0.15ASD; control the electroplating time of the second electroplating tank 401 to be 3-4 hours. The second control device 403 controls the current density and the electroplating time by controlling the electrolytic circuit formed by the first copper-plating magnet 20 and the soluble anode 405.

[0139] The second control device 403 can be implemented in the form of software and / or hardware. For example, in some embodiments, the second control device 403 may include a processor, a controller, etc. In other embodiments, the second control device 403 may include, for example, a PLC (programmable logic controller) program, etc. In some application scenarios, parameters such as the current density and the plating time in the second electroplating tank 401 can be pre-set in the second control device 403, so that the automatic control of the second copper plating system 220 can be achieved. In some other embodiments, the second copper plating system 220 may also include a human-computer interaction interface, which can be directly arranged on the second control device 403, or connected to the second control device 403, so as to display control data and / or facilitate the user to configure the second control device 403.

[0140] In other embodiments, the second copper plating system 220 may further include: a second management tank 402, which may be connected to the second electroplating tank 401; a first liquid replenishing device 406, which may be connected to the second management tank 402, and the first additive may be contained therein; a second liquid replenishing device 407, which may be connected to the second management tank 402, and the second additive may be contained therein; the second control device 403 may also be used to control the first liquid replenishing device 406 and the second liquid replenishing device 407 to respectively add the first additive and the second additive to the second management tank 402, and control the volume ratio of the first additive to the second additive to be 1:2 in each adding operation. In other embodiments, the second control device 403 may control the first liquid replenishing device 406 and the second liquid replenishing device 407 to add the first additive and the second additive to the second electroplating solution once every 50 ampere hours.

[0141] In some embodiments, the volume of the second management tank 402 may be smaller than the volume of the second electroplating tank 401. In other embodiments, the volume of the second management tank 402 may be, for example, 500L. In yet other embodiments, the second management tank 402 may be arranged at a position lower than the second electroplating tank 401, and the second electroplating solution in the second electroplating tank 401 may be transported to the second management tank 402 through a downpipe (e.g., the pipeline where the arrow in the diagram is located), and the second electroplating solution in the second management tank 402 may be transported back to the second electroplating tank 401 through a reflux pipeline connecting the second management tank 402 and the second electroplating tank 401 (e.g., the path indicated by the arrow from the second management tank 402 to the second electroplating tank 401 in the diagram), and the flow of the second electroplating solution may be driven by setting a power device such as a circulating pump on the reflux pipeline. Based on this, the communication between the second management tank 402 and the second electroplating tank 401 can be achieved.

[0142] In some embodiments, the second control device 403 can also be used to: control the temperature of the second plating solution in the second management tank 402 to be 57-63°C; control the pH value of the second plating solution in the second management tank 402 to be 9.4-9.8. Since the temperature of the second plating solution is controlled to be relatively high, a first heating device 404 can be provided in the second management tank 402. In some embodiments, the first heating device 404 can be a heating coil or a heating resistor, etc., and a heat medium such as hot water or hot oil can be introduced into the heating coil to achieve the purpose of heating, or the purpose of heating can be achieved by energizing the heating resistor.

[0143] Controlling the pH value of the second electroplating solution in the second management tank 402 can be achieved by adding a pH regulator to the second management tank 402. In some embodiments, the second copper plating system 220 may further include a pH adding device 408, such as shown in the figure, in which a pH regulator may be contained, so that under the control of the second control device 403, the pH regulator is added to the second management tank 402 in a timely and / or quantitative manner.

[0144] Combination of the above Figure 4 The second copper plating system according to the embodiment of the present disclosure is described exemplarily. It can be understood that the above description and Figure 4 The diagram shown in FIG. 1 is exemplary and not restrictive. For example, the second copper plating system 220 may not be limited to Figure 4 The figure only includes the second electroplating tank 401, the second management tank 402, etc., and other devices may also be included. Figure 5 Provide explanation.

[0145] Figure 5 A schematic diagram of a second copper plating system including a recovery tank according to an embodiment of the present disclosure is shown. Figure 5 As shown in, in some embodiments, the second copper plating system 220 may include a second electroplating tank 401, a second management tank 402, a first recovery tank 501, a second recovery tank 502, and a second control device 403, wherein the second electroplating tank 401 may be a barrel plating tank, the first recovery tank 501 may be used to perform a first cleaning on the electroplating drum, the second recovery tank 502 may be used to perform a second cleaning on the electroplating drum after the first cleaning, and the second control device 403 may control the first recovery tank 501 and the second recovery tank 502. After the electroplating drum is sequentially cleaned for the first cleaning and the second cleaning, a gradient difference in the concentration of the second electroplating solution from large to small is formed between the second electroplating tank 401, the first recovery tank 501, and the second recovery tank 502.

[0146] like Figure 5As further shown in the figure, a liquid level controller 503 may also be provided in the second management tank 402, and the second control device 403 may be connected to the liquid level controller 503, and used to control the liquid level controller 503 and / or receive a liquid level height signal detected by the liquid level controller 503. In some embodiments, the liquid level controller 503 may include a low liquid level detection probe and a medium liquid level detection probe. In some application scenarios, the second control device 403 may be further configured to: in response to the liquid level height of the second electroplating solution in the second management tank 402 being lower than or equal to the low liquid level threshold (i.e., the position of the low liquid level detection probe), the first recovery tank 501 may be controlled to input the liquid in the first recovery tank 501 into the second electroplating tank 401 until the liquid level height of the second electroplating solution in the second management tank 402 reaches the medium liquid level threshold (i.e., the position of the medium liquid level detection probe). The liquid in the first recovery tank 501 may be the liquid after the first cleaning of the electroplating drum. According to such a configuration, the second electroplating solution can be replenished in time by monitoring the liquid level height, thereby effectively reducing the fluctuation range of the copper ion concentration in the second electroplating solution.

[0147] In other embodiments, the liquid level controller 503 may further include a high liquid level detection probe, and the second control device 403 may further be configured to: in response to the liquid level of the second electroplating liquid in the second management tank 402 reaching the high liquid level threshold (i.e., the position of the high liquid level detection probe), control the first recovery tank 501 to stop inputting liquid into the second electroplating tank 401, and / or send out an early warning signal, etc. According to such a setting, the risk of excessive liquid replenishment that may be caused by a failure of the medium liquid level monitoring probe can be avoided, thereby providing double insurance for liquid level monitoring.

[0148] In some other embodiments, a first liquid level controller may also be provided in the first recovery tank 501, and the second control device 403 may control whether the second recovery tank 502 replenishes liquid into the first recovery tank 501 according to the liquid level height signal in the first recovery tank 501 monitored by the first liquid level controller. In some embodiments, a second liquid level controller may be provided in the second recovery tank 502, and the second control device 403 may control whether pure water is replenished into the second recovery tank 502 according to the liquid level height signal in the second recovery tank 502 monitored by the second liquid level controller.

[0149] Compared with directly adding pure water to the second electroplating tank 401, the method of performing step-by-step replenishment by utilizing the concentration gradient difference between the first recovery tank 501, the second recovery tank 502 and the second electroplating tank 401 according to the embodiment of the present disclosure can not only help reduce the impact of the concentration fluctuation of the second electroplating solution in the second electroplating tank 401 during the replenishment process, but also make full use of water resources, that is, pure water only needs to be added to the last-stage recovery tank, without the need to replenish pure water in each stage of the recovery tank.

[0150] Combination of the above Figure 5 The second copper plating system including the recovery tank according to the embodiment of the present disclosure is described exemplarily. It can be understood by those skilled in the art that the above description is exemplary and not restrictive. For example, the number of recovery tanks may not be limited to the two shown in the figure, and may be more or less according to the actual process requirements. It can also be understood that by setting a step-by-step automatic liquid replenishment method, the concentration fluctuation of the second electroplating solution caused by the evaporation of water in the second electroplating tank 401 of the second copper plating system can be effectively controlled, thereby facilitating the effective control of the concentration fluctuation range of the second electroplating solution.

[0151] Figure 6 Schematic diagram of a nickel-phosphorus electroplating system according to an embodiment of the present disclosure is shown. Figure 6 As shown in, the nickel-phosphorus electroplating system 230 may include: a third electroplating tank 601, which may contain a third electroplating solution, the third electroplating solution may include nickel sulfate, A additive and B additive, wherein the concentration of nickel sulfate may be 270-360g / L, the volume content of A additive may be 110-150ml / L, and the volume content of B additive may be 80-120ml / L; A additive may include sodium hypophosphite and phosphoric acid, the mass ratio of sodium hypophosphite to phosphoric acid may be 40-60:1, and the phosphorus content in A additive may be 10-25g / L; B additive may include methanol and sodium citrate, wherein the concentration of sodium citrate in B additive may be 50-100g / L, and the volume content of methanol in B additive may be 1-5ml / L; the volume ratio of A additive to B additive may be 1.5:1.

[0152] The third plating solution is combined with the above Figure 1 Detailed description has been given here, which will not be repeated here. In some embodiments, the third electroplating tank 601 can be a barrel plating tank or a rack plating tank. In other embodiments, the volume of the third electroplating tank 601 can be set to, for example, 3000L. In some other embodiments, a filter can be provided at the open end of the third electroplating tank 601, and the filter can be used to filter the air entering the third electroplating tank 601 to remove impurities in the air entering the third electroplating tank 601.

[0153] In some embodiments, at least one soluble anode 605 may be provided in the third electroplating tank 601, and the at least one soluble anode 605 may form an electrolytic circuit with the second copper-plated magnet 30. The electrolytic circuit may also include circuit components such as a power supply and a rectifier. The nickel-phosphorus electroplating system 230 may also include: a third control device 603, which may be used to: control the current density in the third electroplating tank 601 to be 0.05-0.15ASD; control the electroplating time of the third electroplating tank 601 to be 3-4 hours. In some embodiments, the nickel-phosphorus electroplating treatment may include a first nickel-phosphorus electroplating treatment and a second nickel-phosphorus electroplating treatment, wherein in the first nickel-phosphorus electroplating treatment, the third control device 603 may be further used to control the current density in the third electroplating tank to be 0.10-0.15ASD; in the second nickel-phosphorus electroplating treatment, the third control device 603 may be further used to control the current density in the third electroplating tank to be 0.05-0.10ASD. In other embodiments, the third control device 603 can be further used to control the total electroplating time of the two electroplating nickel-phosphorus treatments to be ≤5.5 hours, such as 5.5 hours, 5 hours, 4.5 hours, 4 hours, 3.5 hours, 3 hours, etc.; preferably, the total electroplating time of the two electroplating nickel-phosphorus treatments is 3-4 hours. The third control device 603 can control the current density and the electroplating time by controlling the electrolysis circuit formed by the second copper-plated magnet 30 and the soluble anode 605.

[0154] The third control device 603 can be implemented in the form of software and / or hardware. For example, in some embodiments, the third control device 603 may include a processor, a controller, etc. In other embodiments, the third control device 603 may include, for example, a PLC (programmable logic controller) program, etc. In some application scenarios, parameters such as the current density and the plating time in the third electroplating tank 601 can be pre-set in the third control device 603, so that the automatic control of the electroplating nickel-phosphorus system 230 can be achieved. In some other embodiments, the electroplating nickel-phosphorus system 230 may also include a human-computer interaction interface, which can be directly arranged on the third control device 603, or connected to the third control device 603, so as to display control data and / or facilitate the user to configure the third control device 603.

[0155] In other embodiments, the nickel-phosphorus electroplating system 230 may further include: a third management tank 602, which may be connected to the third electroplating tank 601; an A agent replenishing device 606, which may be connected to the third management tank 602, and the A additive is contained therein; a B agent replenishing device 607, which may be connected to the third management tank 602, and the B additive is contained therein; the third control device 603 may also be used to control the A agent replenishing device 606 and the B agent replenishing device 607 to respectively replenish the A additive and the B additive into the third management tank 602, and control the replenishing volume ratio of the A additive to the B additive to be 1:2 in each replenishing operation. In still other embodiments, the third control device 603 may control the A agent replenishing device 606 and the B agent replenishing device 607 to replenish the A additive and the B additive into the third electroplating solution once every 20 ampere hours.

[0156] In some embodiments, the volume of the third management tank 602 may be smaller than the volume of the third electroplating tank 601. In other embodiments, the volume of the third management tank 602 may be, for example, 500L. In yet other embodiments, the third management tank 602 may be arranged at a position lower than the third electroplating tank 601, and the third electroplating solution in the third electroplating tank 601 may be transported to the third management tank 602 through a downpipe (e.g., the pipeline where the arrow in the diagram is located), and the third electroplating solution in the third management tank 602 may be transported back to the third electroplating tank 601 through a reflux pipeline connecting the third management tank 602 and the third electroplating tank 601 (e.g., the path indicated by the arrow from the third management tank 602 to the third electroplating tank 601 in the diagram), and the reflux pipeline may be provided with a power device such as a circulating pump to drive the flow of the third electroplating solution. Based on this, the communication between the third management tank 602 and the third electroplating tank 601 can be achieved.

[0157] In some embodiments, the third control device 603 can also be used to: control the temperature of the third electroplating solution in the third management tank 602 to be 47-53°C; control the pH value of the third electroplating solution in the third management tank 602 to be 2-2.6. Since the temperature of the third electroplating solution is controlled to be higher than room temperature, a second heating device 604 can be set in the third management tank 602. In some embodiments, the second heating device 604 can be a heating coil or a heating resistor, etc., and a heat medium such as hot water or hot oil can be passed into the heating coil to achieve the purpose of heating, or the purpose of heating can be achieved by energizing the heating resistor. In other embodiments, the electroplating nickel-phosphorus treatment can include a first electroplating nickel-phosphorus treatment and a second electroplating nickel-phosphorus treatment, and the third control device 603 can be further used to: in the first electroplating nickel-phosphorus treatment, control the pH value of the third electroplating solution in the third management tank 602 to be 2.3-2.6; in the second electroplating nickel-phosphorus treatment, control the pH value of the third electroplating solution in the third management tank to be 2.0-2.3.

[0158] Controlling the pH value of the third electroplating solution in the third management tank 602 can be achieved by adding a pH regulator to the third management tank 602. In some embodiments, the nickel-phosphorus electroplating system 230 may further include, for example, a pH replenishing device, which may contain a pH regulator so that under the control of the third control device 603, the pH regulator is added to the third management tank 602 in a timely and / or quantitative manner.

[0159] In other embodiments, the nickel-phosphorus electroplating system 230 may further include: a nickel ion online analysis device 609, which may be connected to the third management tank 602 and used to monitor the nickel concentration of the third electroplating solution in the third management tank 602; and a nickel replenishing device 608, which may be connected to the third management tank 602 and may contain a nickel sulfate solution; the third control device 603 may also be used to control the nickel replenishing device 608 to replenish the nickel sulfate solution into the third management tank 602 when the nickel concentration in the third electroplating solution is lower than 60 g / L, so that the nickel concentration in the third electroplating solution is maintained at 60-80 g / L.

[0160] In some embodiments, the nickel ion online analyzer 609 may include a titration analyzer, etc. In other embodiments, the nickel ion online analyzer 609 may continuously measure the nickel ion concentration in the third electroplating solution by a spectrophotometric measurement method. When the third control device 603 controls the nickel replenishing device 608 to replenish the nickel sulfate solution in the third management tank 602, it may control the opening and closing of the nickel replenishing device 608 in real time according to the nickel ion concentration monitored by the nickel ion online analyzer 609. According to such a setting, the nickel ion concentration in the third electroplating solution can be controlled to fluctuate within a smaller range, thereby ensuring the basic stability of the nickel ion concentration.

[0161] Example

[0162] In order to make it easier to understand the preparation method of the NdFeB magnet of the disclosed embodiment, it will be described below in conjunction with specific examples. In the following examples, a roller plating process is used, and 50,000 NdFeB magnet products can be produced in one roller. That is to say, one batch can produce 50,000 NdFeB magnet products at the same time. In each batch of production, the NdFeB magnet matrix is ​​subjected to a first copper plating treatment, a second copper plating treatment and an electroplating nickel-phosphorus treatment to obtain a NdFeB magnet product. In the following embodiments, ten batches of products are continuously produced using the preparation process conditions shown in Table 1, Table 2 and Table 6, and 32 products are sampled in each batch for testing. Examples 1-16 are all examples of preparation process conditions including a single electroplating nickel-phosphorus treatment, and Examples 17-18 are examples of preparation process conditions including two electroplating nickel-phosphorus treatments. Table 6 only shows the process conditions of Examples 17-18 that are different from Example 3, that is, the other process conditions not shown in Table 6 are the same as those in Example 3.

[0163] The test results of each embodiment are shown in Table 3, Table 4, Table 5 and Table 7, wherein after the first copper plating treatment, the sample was taken out to test the glossiness and thickness of the base copper plating layer; after the second copper plating treatment, the sample was taken out to test the glossiness and thickness of the electroplated copper layer, and the final product sample was subjected to a hundred-grid test, a salt spray test and a phosphorus content test. The present disclosure also selected product samples of Example 3 and Example 9 for CP value detection to evaluate the stability of the plating thickness and glossiness of mass-produced products. The present disclosure also conducted electroplated nickel phosphorus layer thickness detection, phosphorus content detection, hundred-grid test, salt spray test, etc. on the product samples of Example 17-Example 18, and the results are shown in Table 7.

[0164] Table 1:

[0165]

[0166]

[0167] Table 2:

[0168]

[0169]

[0170]

[0171] Table 3:

[0172]

[0173]

[0174] Table 4:

[0175]

[0176]

[0177] Table 5:

[0178]

[0179] Table 6:

[0180]

[0181] Table 7:

[0182]

[0183]

[0184] Among them, the coating thickness is measured by using an X-ray thickness gauge to measure any three different parts of a single product, and the average value of the coating thickness of these three different parts is taken as the coating thickness value of a single product. The surface gloss measurement is measured by using a Novo-Curve Glossmeter measuring instrument, and the measuring angle is 60°. The salt spray test (SST) conditions are: temperature of 40°C, concentration of 5% salt solution, spray speed of 2ml / h, pH value of 6.8-7.2.

[0185] The test of the phosphorus content of the coating is achieved by combining a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS). EDS can measure the composition of the elements on the surface of the product while the SEM scans the surface of the product. That is, the phosphorus content in this article refers to the phosphorus content on the surface of the coating, which is obtained by measuring the average phosphorus content on the surface of the coating by SEM's EDS. For example, for a NdFeB magnet product including a single-layer electroplated nickel-phosphorus layer, the surface of the electroplated nickel-phosphorus layer can be measured after the electroplating nickel-phosphorus treatment is completed to obtain the phosphorus content on its surface. For a NdFeB magnet product including multiple layers of electroplated nickel-phosphorus layers, the surface of the current electroplated nickel-phosphorus layer can be measured after each electroplating nickel-phosphorus treatment is completed, so that the phosphorus content on the surface of each electroplated nickel-phosphorus layer can be obtained.

[0186] CP, short for Process Capability index, is an engineering capability index that indicates the actual processing capability of a process in a stable state over a certain period of time. CP = (maximum value - minimum value) / (6 * Stdev); Stdev refers to the estimated standard deviation based on the sample, which reflects the degree of dispersion of the value relative to the mean.

[0187] The grid test uses a blade of specific specifications to make an X-shaped cut of 1x1mm on the product's plated surface at a certain angle with appropriate pressure, covers the X-shaped cut of the product with tape, and presses the tape flat in the cut area with your fingers. Within 120s of applying the tape, hold the suspended end of the tape and quickly tear off the tape at an angle as close to 180° as possible. By checking the peeling area of ​​the coating, the adhesion between the coating and the substrate (i.e. the bonding strength between the bottom copper coating and the substrate) is determined.

[0188] From the above test results we can see that:

[0189] (1) From the results of the 100-grid test, when other process conditions are the same or similar (for example, compared to any one of Examples 1-3), there is a risk of 100-grid failure when the impact current is not used in Example 13 and when the impact current is not used before the first copper plating treatment in Example 4, which indicates that the use of impact current is beneficial to enhancing the bonding force between the bottom copper plating layer and the substrate. For Example 13, since the initial electroplating speed is slow when there is no impact current, the electroplated copper layer of some products may be corroded by the nickel-phosphorus solution, resulting in rust spots on the surface of the plating layer, which may affect the appearance qualification rate (i.e., the glossiness of the finished product) and salt spray effect (i.e., corrosion resistance) of some products.

[0190] (2) It can be seen from the test results of Example 5 that when the copper ion content in the first electroplating solution is greater than 3 g / L, an adverse effect is exerted on the bonding force between the coating and the substrate. This may be because a higher copper ion content in the first electroplating solution will increase the probability of a replacement reaction; at the same time, a higher copper ion concentration will also lead to a faster electroplating speed, resulting in an increase in the coating thickness at the same ampere-hour.

[0191] (3) It can be seen from the test results in Table 5 that, compared with the case where only a full copper anode is used in the first electroplating solution without an insoluble anode (such as Example 9), the use of both a copper anode and an insoluble anode in the first electroplating solution (such as Example 3) makes the CP value of the thickness of each layer of the plating layer of the mass-produced products higher and the CP value of the glossiness is also higher, indicating that the use of both a copper anode and an insoluble anode is beneficial to improving the stability of the plating layer thickness and the glossiness of the products in mass production.

[0192] (4) It can be seen from the test results of Example 6 that when the phosphorus content in the third electroplating solution is low, the phosphorus content on the electroplated nickel phosphorus layer is reduced, which will affect the salt spray effect of the product, that is, affect the corrosion resistance of the product.

[0193] (5) From the test results of Examples 7 and 8, it can be seen that as the temperature of the first electroplating solution increases, the results of the hundred-grid test are poor, which indicates that the temperature has a greater influence on the bonding force between the coating and the substrate. This may be due to the fact that the probability of the replacement reaction is greatly increased as the temperature increases. In addition, the high temperature of the first electroplating solution will also lead to a faster electroplating speed, which will significantly increase the thickness of the bottom copper coating, and thus cause the total thickness of the electroplated copper layer of some products (see the maximum value) to be greater than 4 μm, and the glossiness of the finished product will also exceed the appropriate range.

[0194] (6) From the test results of Example 10, compared with the preparation method including pretreatment, the glossiness of the bottom copper plating layer of the product produced by the preparation method without pretreatment is lower, which in turn affects the glossiness of the entire product. At the same time, there is also a risk of failing the 100-grid test, which indicates that the pretreatment process has a certain influence on the bottom copper plating layer, which is beneficial to improving the bonding strength between the bottom copper plating layer and the substrate.

[0195] (7) From the test results of Example 11 and Example 12, it can be seen that the nickel ion content in the third electroplating solution is too high, and there is a risk of failing the salt spray test, that is, affecting the corrosion resistance of the finished product. If the nickel ion content in the third electroplating solution is too low, it may affect the electroplating speed, resulting in a decrease in the thickness of the coating obtained at the same electroplating time, and then the electroplating time required for the same coating thickness is increased, which may affect the product output.

[0196] (8) According to the test results of Example 14, when the starting ratio of the first additive to the second additive exceeds 1:4, the glossiness of the product may be affected.

[0197] (9) From the test results of Example 15, it can be seen that in the second copper plating treatment, the copper ion concentration is too high, which will lead to a higher total thickness of the electroplated copper layer, and the total thickness of the electroplated copper layer of some products (see the maximum value) is greater than 4 μm; at the same time, the glossiness is too high, which will affect the product's ability to be optically recognized.

[0198] (10) From the test results of Example 16, it can be seen that the content of sodium citrate in the third electroplating solution is too little, which will affect the phosphorus content of the product, making the phosphorus content of the product lower, which may affect the corrosion resistance of the product.

[0199] (11) From the test results in Table 7, it can be seen that the NdFeB magnet products made by the double-layer nickel-phosphorus electroplating process can still ensure a relatively thin coating thickness and can pass the 100-grid test and the 96-hour salt spray test, indicating that the NdFeB magnet products with double-layer nickel-phosphorus electroplating have significant corrosion resistance.

[0200] Figure 7 FIG. 2 shows an electron microscope image of any magnet product sample prepared in Example 3 of the present disclosure. Figure 7As shown in FIG. 1 , the coating formed on the surface of the NdFeB magnet includes an electroplated copper layer 701 and an electroplated nickel-phosphorus layer 702. Although the two-step copper plating is used in the embodiment of the present disclosure, Figure 7 It can be seen that the two copper layers are well fused together, indicating that the two copper layers have good bonding strength.

[0201] By comparing the appearance of some magnet product samples prepared in Example 3 of the present disclosure with the appearance of some magnet product samples prepared in Example 16, it can be found that the sodium citrate content in Example 16 is relatively low, which causes problems such as white spots and uneven gloss on the appearance of some products produced. This may be due to the uneven distribution of crystalline particles of the electroplated nickel-phosphorus layer of the product, which increases the defective rate of the product appearance. In comparison, when the sodium citrate content is within a suitable range, such as in Example 3, the appearance of the produced product is more uniform and beautiful, which may be due to the more delicate and uniform crystalline particles of the electroplated nickel-phosphorus layer, which significantly reduces the defective rate of the product appearance.

[0202] Although multiple embodiments of the present disclosure have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art may think of many changes, modifications, and alternatives without departing from the thought and spirit of the present disclosure. It should be understood that in the process of practicing the present disclosure, various alternatives to the embodiments of the present disclosure described herein may be adopted. The attached claims are intended to define the scope of protection of the present disclosure, and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A method for preparing a neodymium iron boron magnet, comprising: Placing the NdFeB magnet substrate in a first electroplating solution for a first copper plating treatment to form a first copper-plated magnet; Placing the first copper-plated magnet in a second electroplating solution for a second copper plating treatment to form a second copper-plated magnet; as well as The second copper-plated magnet is placed in a third electroplating solution for nickel-phosphorus electroplating to form a neodymium-iron-boron magnet including multiple electroplating layers.

2. The preparation method according to claim 1, wherein the third electroplating solution comprises nickel sulfate, additive A and additive B, wherein the concentration of the nickel sulfate is 270-360 g / L, the volume content of the additive A is 110-150 ml / L, and the volume content of the additive B is 80-120 ml / L; The A additive comprises at least one of phosphate, phosphite, hypophosphite, phosphoric acid, and phosphorous acid, and the phosphorus content of the A additive is 10-25 g / L; The B additive includes methanol and sodium citrate, wherein the concentration of sodium citrate in the B additive is 50-100 g / L, and the volume content of the methanol in the B additive is 1-5 ml / L; Preferably, the A additive comprises sodium hypophosphite and phosphoric acid, and the mass ratio of the sodium hypophosphite to the phosphoric acid is 40-60:1; Preferably, when the nickel-phosphorus electroplating treatment is started, the volume ratio of the A additive to the B additive in the third electroplating solution is 1.5:

1.

3. The preparation method according to claim 2, further comprising: During the nickel-phosphorus electroplating treatment process, the A additive and the B additive are added to the third electroplating solution once or multiple times, and the volume ratio of the A additive to the B additive in each adding operation is 1:2; Preferably, the A additive and the B additive are added to the third electroplating solution in proportion every 20 ampere hours.

4. The preparation method according to any one of claims 1 to 3, wherein the control conditions of the nickel-phosphorus electroplating treatment include: Controlling the temperature of the third electroplating solution to be 47-53° C. and the pH value to be 2-2.6; Preferably, the current density of the nickel-phosphorus electroplating treatment is controlled to be 0.05-0.15 ASD, and the electroplating time is 3-4 hours.

5. The preparation method according to any one of claims 1 to 3, wherein placing the second copper-plated magnet in a third electroplating solution for nickel-phosphorus electroplating treatment comprises: Placing the second copper-plated magnet in the third electroplating solution for a first nickel-phosphorus electroplating treatment to form a neodymium-iron-boron magnet including a first nickel-phosphorus electroplating layer; as well as The NdFeB magnet including the first electroplated NiP layer is placed in the third electroplating solution for a second NiP electroplating treatment to form a NdFeB magnet including the first electroplated NiP layer and the second electroplated NiP layer.

6. The preparation method according to claim 5, wherein: In the first nickel-phosphorus electroplating treatment, the pH value of the third electroplating solution is controlled to be 2.3-2.6; In the second nickel-phosphorus electroplating treatment, the pH value of the third electroplating solution is controlled to be 2.0-2.3; Preferably, the current density of the first nickel-phosphorus electroplating treatment is controlled to be 0.10-0.15 ASD, and the current density of the second nickel-phosphorus electroplating treatment is controlled to be 0.05-0.10 ASD.

7. The preparation method according to claim 2, wherein during the nickel-phosphorus electroplating treatment, the preparation method further comprises: monitoring the nickel concentration in the third electroplating solution; and When the nickel concentration is lower than 60 g / L, nickel sulfate is added to the third electroplating solution so that the nickel concentration in the third electroplating solution is maintained at 60-80 g / L.

8. The preparation method according to claim 1, further comprising: Disposing at least one anode copper plate and at least one first insoluble anode in the first electroplating solution to form a first electrolysis circuit with the NdFeB magnet matrix; Disposing at least one second insoluble anode and at least one cathode in the first electroplating solution to form a second electrolysis loop; and During the first copper plating process, the second electrolytic circuit is controlled to be turned on and off according to the copper ion concentration in the first electroplating solution.

9. The preparation method according to claim 8, wherein controlling the opening and closing of the second electrolytic circuit according to the copper ion concentration in the first electroplating solution comprises: In response to the copper ion concentration in the first electroplating solution being less than 2.2 g / L, closing the second electrolysis circuit; In response to the copper ion concentration in the first electroplating solution being greater than 2.4 g / L, the second electrolysis circuit is started.

10. The preparation method according to claim 1, wherein the first electroplating solution comprises a copper salt, 80-140 g / L of a complexing agent and 2-4 ml / L of a wetting agent solution, and the copper ion concentration in the first electroplating solution is 2-3 g / L; Preferably, the wetting agent solution comprises a solution of sodium alkyl ether phosphate, and the concentration of the solution of sodium alkyl ether phosphate is 5-10 wt %.

11. The preparation method according to claim 1, wherein the control conditions of the first copper plating process include: Controlling the temperature of the first electroplating solution to be 17-23° C. and the pH value to be 9.6-10; as well as The electroplating time of the first copper plating treatment is controlled to be 1-2 hours, and the current density is controlled to be 0.05-0.15ASD.

12. The preparation method according to claim 1, wherein the second electroplating solution comprises a copper salt, a complexing agent, a first additive and a second additive, wherein: The copper ion concentration in the second electroplating solution is 8.5-9.5 g / L; The concentration of the complexing agent is 110-170 g / L; The first additive comprises 1-5wt% of anhydrous bismuth nitrate, 1-5wt% of glycine and 1-10wt% of potassium carbonate in a mass ratio; The second additive comprises 1-10wt% sodium chlorite and 1-10wt% sodium sulfate; When the second copper plating treatment begins, the volume ratio of the first additive to the second additive in the second electroplating solution is 1:4, and the volume content of the second additive in the second electroplating solution is 7-9 ml / L.

13. The preparation method according to claim 12, further comprising: In the second copper plating process, the first additive and the second additive are added to the second electroplating solution once or multiple times, and the volume ratio of the first additive to the second additive in each adding operation is 1:2; Preferably, the first additive and the second additive are added to the second plating solution in proportion every 50 ampere hours.

14. The preparation method according to claim 1, wherein the control conditions of the second copper plating process include: Controlling the temperature of the second electroplating solution to be 57-63° C. and the pH value to be 9.4-9.8; as well as The electroplating time of the second copper plating treatment is controlled to be 3-4 hours, and the current density is controlled to be 0.05-0.15ASD.

15. The preparation method according to claim 1, wherein: Before performing at least one of the first copper plating treatment, the second copper plating treatment and the nickel-phosphorus electroplating treatment, a shock current is applied, the magnitude of the shock current is 1.4-2 times the magnitude of the current during electroplating, the first copper plating treatment or the second copper plating treatment applies the shock current for 10-30 minutes, or the nickel-phosphorus electroplating treatment applies the shock current for 20-50 minutes.

16. A neodymium iron boron magnet prepared according to the preparation method according to any one of claims 1 to 15.

17. A neodymium iron boron magnet, comprising: NdFeB magnet matrix; An electroplated copper layer, which is attached to the surface of the NdFeB magnet substrate, wherein the thickness of the electroplated copper layer is ≤4 μm and the thickness tolerance is ±1 μm; as well as An electroplated nickel-phosphorus layer is attached to the electroplated copper layer, wherein the thickness of the electroplated nickel-phosphorus layer is ≤3 μm and the thickness tolerance is ±1 μm.

18. The NdFeB magnet according to claim 17, wherein: The total thickness of the electroplated copper layer and the electroplated nickel-phosphorus layer is ≤7 μm; Preferably, the total thickness of the electroplated copper layer and the electroplated nickel-phosphorus layer is 3-7 μm.

19. The NdFeB magnet according to any one of claims 17-18, wherein: The phosphorus content of the electroplated nickel-phosphorus layer is ≥ 11wt%; Preferably, the electroplated nickel-phosphorus layer comprises a first electroplated nickel-phosphorus layer and a second electroplated nickel-phosphorus layer, and the thickness of the first electroplated nickel-phosphorus layer is 1-2 μm, and the thickness of the second electroplated nickel-phosphorus layer is 0.5-1 μm; Preferably, the phosphorus content of the first electroplated nickel-phosphorus layer is 9-12 wt %, and the phosphorus content of the second electroplated nickel-phosphorus layer is 12-14 wt %.

20. The NdFeB magnet according to any one of claims 17 to 19, wherein: The electroplated copper layer includes a bottom copper plating layer and a thick copper plating layer, wherein the bottom copper plating layer is attached to the surface of the NdFeB magnet substrate, the thick copper plating layer is located between the bottom copper plating layer and the electroplated nickel-phosphorus layer, and the bottom copper plating layer has a thickness of 0.8-1.2 μm.

21. The NdFeB magnet according to any one of claims 17 to 19, wherein the surface glossiness is 100-200 GU.

22. A system for preparing a neodymium iron boron magnet, comprising: A first copper plating system is used to perform a first copper plating process on the NdFeB magnet substrate to form a first copper-plated magnet; A second copper plating system, used for performing a second copper plating process on the first copper-plated magnet to form a second copper-plated magnet; as well as The nickel-phosphorus electroplating system is used to perform nickel-phosphorus electroplating on the second copper-plated magnet to form a neodymium-iron-boron magnet including multiple electroplating layers.

23. The system of claim 22, wherein the nickel phosphorus electroplating system comprises: a third electroplating tank, containing a third electroplating solution therein, wherein the third electroplating solution comprises nickel sulfate, an A additive and a B additive, wherein the concentration of the nickel sulfate is 270-360 g / L, the volume content of the A additive is 110-150 ml / L, and the volume content of the B additive is 80-120 ml / L; The A additive comprises at least one of phosphate, phosphite, hypophosphite, phosphoric acid, and phosphorous acid, and the phosphorus content of the A additive is 10-25 g / L; The B additive includes methanol and sodium citrate, wherein the concentration of sodium citrate in the B additive is 50-100 g / L, and the volume content of the methanol in the B additive is 1-5 ml / L; Preferably, the A additive comprises sodium hypophosphite and phosphoric acid, and the mass ratio of the sodium hypophosphite to the phosphoric acid is 40-60:1; Preferably, the volume ratio of the A additive to the B additive is 1.5:1; Preferably, the current density in the third electroplating tank is 0.05-0.15ASD, and the electroplating time of the third electroplating tank is controlled to be 3-4 hours; Preferably, the nickel-phosphorus electroplating treatment includes a first nickel-phosphorus electroplating treatment and a second nickel-phosphorus electroplating treatment, wherein in the first nickel-phosphorus electroplating treatment, the current density in the third electroplating tank is 0.10-0.15ASD; in the second nickel-phosphorus electroplating treatment, the current density in the third electroplating tank is 0.05-0.10ASD.

24. The system of claim 23, wherein the nickel phosphorus electroplating system further comprises: A third management tank, which is connected to the third electroplating tank; A liquid replenishing device, which is connected to the third management tank and contains the A additive; A B agent replenishing device, which is connected to the third management tank and contains the B additive; A third control device, which is used to control the A agent replenishing device and the B agent replenishing device to replenish the A additive and the B additive to the third management tank respectively, and in each replenishing operation, the replenishing volume ratio of the A additive to the B additive is controlled to be 1:2; Preferably, the third control device controls the agent A replenishing device and the agent B replenishing device to replenish the additive A and the additive B into the third electroplating solution once every 20 ampere hours.

25. The system according to claim 24, wherein the third control device is further configured to: Controlling the temperature of the third electroplating solution in the third management tank to be 47-53° C.; The pH value of the third electroplating solution in the third management tank is controlled to be 2-2.

6.

26. The system according to claim 24 or 25, wherein the nickel-phosphorus electroplating process comprises a first nickel-phosphorus electroplating process and a second nickel-phosphorus electroplating process, and the third control device is further used for: In the first nickel-phosphorus electroplating treatment, the pH value of the third electroplating solution in the third management tank is controlled to be 2.3-2.6; In the second nickel-phosphorus electroplating treatment, the pH value of the third electroplating solution in the third management tank is controlled to be 2.0-2.

3.

27. The system according to any one of claims 24-26, wherein the nickel-phosphorus electroplating system further comprises: A nickel ion online analysis device, which is connected to the third management tank and is used to monitor the nickel concentration of the third electroplating solution in the third management tank; as well as A nickel supplement device, which is connected to the third management tank and contains a nickel sulfate solution; The third control device is also used to control the nickel replenishing device to replenish nickel sulfate solution into the third management tank when the nickel concentration in the third electroplating solution is lower than 60g / L, so that the nickel concentration in the third electroplating solution is maintained at 60-80g / L.

28. The system of claim 22, wherein the first copper plating system comprises: A first electroplating tank, containing a first electroplating solution, wherein the first electroplating solution comprises a copper salt, 80-140 g / L of a complexing agent and 2-4 ml / L of a wetting agent solution, wherein the copper ion concentration in the first electroplating solution is 2-3 g / L; Preferably, the wetting agent solution comprises a solution of sodium alkyl ether phosphate, and the concentration of the solution of sodium alkyl ether phosphate is 5-10 wt %.

29. The system according to claim 28, wherein at least one anode copper plate and at least one first insoluble anode are disposed in the first electroplating tank to form a first electrolytic circuit with the NdFeB magnet matrix; The first copper plating system also includes: A first control device is used to: Controlling the current density in the first electrolysis loop to be 0.05-0.15 ASD; The electroplating time of the first electrolytic circuit is controlled to be 3-4 hours.

30. The system of claim 29, wherein the first copper plating system further comprises: A first management tank, which is in communication with the first electroplating tank and has at least one second insoluble anode and at least one cathode disposed therein to form a second electrolysis circuit; as well as a copper ion analysis device, connected to the first management tank, for detecting the copper ion concentration in the first electroplating solution in the first management tank; and The first control device is also used to control the opening and closing of the second electrolysis circuit according to the copper ion concentration in the first electroplating solution.

31. The system of claim 30, wherein the first control device is further configured to: In response to the copper ion concentration in the first electroplating solution being less than 2.2 g / L, closing the second electrolysis circuit; In response to the copper ion concentration in the first electroplating solution being greater than 2.4 g / L, the second electrolysis circuit is started.

32. The system according to claim 30 or 31, wherein the first control device is further configured to: Controlling the temperature of the first electroplating solution in the first management tank to be 17-23° C.; The pH value of the first electroplating solution in the first management tank is controlled to be 9.6-10.

33. The system of claim 22, wherein the second copper plating system comprises: The second electroplating tank contains a second electroplating solution, wherein the second electroplating solution includes a copper salt, a complexing agent, a first additive and a second additive, wherein: The copper ion concentration in the second electroplating solution is 8.5-9.5 g / L; The concentration of the complexing agent is 110-170 g / L; The first additive comprises 1-5wt% of anhydrous bismuth nitrate, 1-5wt% of glycine and 1-10wt% of potassium carbonate in a mass ratio; The second additive comprises 1-10wt% sodium chlorite and 1-10wt% sodium sulfate; The volume ratio of the first additive to the second additive is 1:4, and the volume content of the second additive in the second electroplating solution is 7-9 ml / L.

34. The system of claim 33, wherein the second copper plating system further comprises: A second management tank, which is in communication with the second electroplating tank; a first liquid replenishing device, which is connected to the second management tank and contains the first additive; a second liquid replenishing device, which is connected to the second management tank and contains the second additive; A second control device, which is used to control the first liquid replenishing device and the second liquid replenishing device to replenish the first additive and the second additive to the second management tank respectively, and in each replenishing operation, controls the replenishing volume ratio of the first additive to the second additive to be 1:2; Preferably, the second control device controls the first liquid replenishing device and the second liquid replenishing device to replenish the first additive and the second additive into the second electroplating solution once every 50 ampere hours.

35. The system of claim 34, wherein the second control device is further configured to: Controlling the temperature of the second electroplating solution in the second management tank to be 57-63° C.; Controlling the pH value of the second electroplating solution in the second management tank to be 9.4-9.8; and The electroplating time of the second electroplating tank is controlled to be 3-4 hours, and the current density is controlled to be 0.05-0.15ASD.

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