WO2016161742A1 - Method for improving performance of modification layer of material surface and application thereof - Google Patents

Abstract

Provided is a method for improving performance of a modification layer of a material surface. The method comprises: coating an inorganic zinc-silicon rich sol-gel on a material surface to be processed to form a priming coating, and coating a zinc chromate coating liquid on the priming coating to form a zinc chromate membrane. The inorganic zinc-silicon rich sol-gel comprises a soluble alkali metal silicate material, an inorganic gel and ultrafine zinc powder, and the zinc chromate coating liquid comprises sheet-like zinc powder, aluminum powder, a chromic anhydride, a boronic acid and a surfactant, etc. Also provided is an application of the method in an aspect of magnet protection to obtain a permanent magnet and a device comprising the same. The method has a simple process, easy control, low costs, is safe and environmentally friendly, and suitable for processing various NdFeB permanent magnets.

Description

Method for improving performance of surface modification layer of material and application thereof Technical field

The invention relates to a surface treatment technology of materials, in particular to a method for improving the comprehensive performance of a rare earth permanent magnet material, such as a surface protection layer of a neodymium iron boron magnet, and belongs to the technical field of surface modification of materials.

Background technique

NdFeB permanent magnet materials have been widely used in voice coil motors, magnetic resonance imaging, general motors, generators, sensors, meters, etc. due to their excellent magnetic properties. However, the poor corrosion resistance of NdFeB itself has seriously affected its application, so the anti-corrosion research of NdFeB is of great significance. At present, although many methods for protecting NdFeB magnets have been developed, sintered NdFeB magnets have a large number of pores, which tend to leave acid and plating liquids, causing long-term corrosion of magnets and coatings. The pores of the magnet may also cause electrodeposition defects, which may cause hydrogen embrittlement during pickling or electroplating to cause coating damage, weaken the shielding effect of the metal deposition layer, and make the magnet easy to be powdered or peeled off during use. Although the dry plating technique avoids some shortcomings of the wet plating technique, the cost is high, and the shape and size of the magnet are required to be high. From the perspective of the magnet user, the corrosion prevention problem of the magnet is far from solved.

Zinc-chromium coating technology is a new surface treatment technology that is completely closed and does not produce waste water and exhaust gas pollution. The zinc-chromium coating liquid used therein has better coating ability, can be dip-coated, brush-coated, spray-coated, can be processed on the inside and outside of complex parts, and has a thin film and a simple processing process, which does not affect the processing precision. It also has little impact on costs. The formed zinc-chromium film has no hydrogen embrittlement, good corrosion resistance and solderability compared with the ordinary plating layer. In recent years, the anti-corrosion technology of zinc-chromium metal surface has been used as a substitute for many traditional anti-corrosion treatment processes such as electroplating, hot dip galvanizing, electroplating cadmium, zinc-based alloy plating and phosphating. Moreover, the technology has gradually expanded from the automotive industry to construction, power, railway, home appliances, military and other applications.

However, the bonding strength between the single zinc-chromium film formed by the zinc-chromium film coating technology and the substrate is poor, and the weather resistance and wear resistance are also weaker than the conventional plating. In addition, the zinc-chromium film coating technology has rarely been reported in the anti-corrosion application of NdFeB magnets, and has not yet been adapted to practical use.

Summary of the invention

The main object of the present invention is to provide a method for improving the performance of a surface modification layer of a material to overcome the prior art. foot.

Another object of the present invention is to provide an application of the method of improving the properties of a surface modification layer of a material.

In order to achieve the foregoing object, the technical solution adopted by the present invention includes:

A method for improving the performance of a surface modification layer of a material, comprising:

Applying an inorganic zinc-rich silica sol to the surface of the material to be treated to form a primer layer,

And coating a zinc chromium coating solution on the primer layer to form a zinc chromium film;

The inorganic zinc-rich silica sol comprises a soluble alkali metal silicate material, an inorganic gel and an ultrafine zinc powder.

The zinc chromium coating liquid includes flake zinc powder, aluminum powder, chromic anhydride, boric acid, a surfactant, a pH adjuster, and deionized water.

In a preferred embodiment, the preparation process of the inorganic zinc-rich silica sol comprises: mixing the inorganic gel with the soluble alkali metal silicate material, adding a silane coupling agent and a pH adjuster, and mixing the solution. The pH is controlled at 4 to 5.5 while continuously stirring until the mixed solution is in the form of a translucent colloid, after which the ultrafine zinc powder is added.

Further, the soluble alkali metal silicate material includes any one or a combination of two or more of sodium water glass, potassium water glass, and lithium water glass, but is not limited thereto.

In a preferred embodiment, the inorganic zinc-rich silica sol comprises from 2 to 10% by weight of an inorganic gel.

Further, the inorganic gel includes potassium silicate and/or zinc silicate, but is not limited thereto.

In a preferred embodiment, the ultrafine zinc powder has a particle size of 3.2 to 4 μm.

In a preferred embodiment, the inorganic zinc-rich silica sol further comprises from 0.8 to 5 wt% of an adjuvant.

Further, the auxiliary agent includes a silane coupling agent, but is not limited thereto.

Further, the pH adjuster includes ZnO and/or CaO, but is not limited thereto.

In a preferred embodiment, the mass ratio of the total amount of the inorganic zinc-rich silica sol to the zinc powder is 1:2 to 4.

In a preferred embodiment, the zinc chromium coating solution comprises 15 to 35 wt% of flake zinc powder, 3 to 10 wt% of aluminum powder, 2.5 to 8 wt% of chromic anhydride, 0.5 to 1.5 wt% of boric acid, 0.5 to 1 wt. % surfactant, 0.6 to 2 wt% reducing agent, 1 to 1.8 wt% pH adjuster, 10 to 25 wt% auxiliary.

Further, the surfactant includes any one of polyoxyethylene nonylphenol and divinyl alcohol, or a combination of two or more thereof, but is not limited thereto.

Further, the reducing agent includes any one or a combination of two or more of succinic acid, acrylic acid, and fatty acid, but is not limited thereto.

Further, the auxiliary agent includes glycerin and/or hydroxyethyl cellulose, but is not limited thereto.

In a preferred embodiment, the flake zinc powder is an analytically pure zinc powder having a thickness of 0.2 to 0.3 μm and an average particle diameter of 4 to 6 μm.

In a preferred embodiment, the flake aluminum powder is an analytically pure flake aluminum powder having a thickness of 0.2 to 0.3 μm and an average particle diameter of 4 to 6 μm.

In a preferred embodiment, the zinc chromium coating solution has a pH of 4.5 to 6.

In a preferred embodiment, the method for preparing the zinc chromium coating solution comprises: firstly mixing zinc powder, aluminum powder, surfactant and auxiliary agent in proportion to form a uniformly dispersed zinc aluminum paste, and then sequentially adding chromium. The anhydride and boric acid are continuously stirred, and then the pH adjuster and deionized water are added to adjust the pH and viscosity of the slurry. After the mixture to be formed is uniformly layered, the reducing agent is slowly added, and the stirring speed is required to be accelerated during the addition. After the addition of the reducing agent is completed, the stirring is continued for 30 minutes or more to stabilize the formed mixture.

In a preferred embodiment, the method for improving the performance of a surface modification layer of a material comprises:

Spraying the inorganic zinc-rich silica sol onto the surface of the material to be treated by a spray gun to form a primer layer, wherein the pressure of the spray gun is 3-6 MPa, and the working interval between the spray gun and the magnet is 10-20 cm;

And drying the bottom layer, wherein the drying temperature is 40 to 80 ° C, the drying time is 10 to 30 minutes, and then the zinc chromium coating liquid is applied.

More preferably, the method for improving the performance of the surface modification layer of the material comprises:

Spraying the zinc-chromium coating liquid on the primer layer by a spray gun to form a coating layer, wherein the pressure of the spray gun is 2 to 4 MPa, and the working interval between the spray gun and the magnet is 15 to 20 cm;

And preheating and drying the coating, wherein the preheating drying treatment temperature is 60 to 120 ° C, the time is 10 to 30 minutes, and then curing treatment is performed, the curing temperature is 280 to 300 ° C, and the processing time is 15 ~40 minutes.

Preferably, the method for improving the performance of the surface modification layer of the material further comprises:

After the preheating drying treatment is completed, the temperature is raised to a curing temperature at a temperature rising rate of 5 ° C to 20 ° C / minute, and curing treatment is performed.

In a preferred embodiment, the method for improving the performance of the surface modification layer of the material comprises: pretreating the surface of the material to be treated, and then coating the surface of the material to be treated with an inorganic zinc-rich silica sol; the pretreatment includes Degreasing, descaling, polishing and cleaning.

A surface modification layer produced by any of the foregoing methods for improving the properties of the surface modification layer of the material.

A method for protecting a surface of a magnet, comprising:

Providing a magnet and pretreating the surface of the magnet;

And, a protective layer is formed on the surface of the magnet by any of the foregoing methods for improving the properties of the surface modification layer of the material.

Further, the magnet includes a neodymium iron boron permanent magnet, but is not limited thereto.

More preferably, the NdFeB permanent magnet has a grain size of 3 to 10 μm.

In a preferred embodiment, the pre-processing includes:

Degreasing, comprising: removing oil stain on the surface of the permanent magnet with an organic solvent and/or an alkali solution;

Derusting, including: surface rust removal and descaling treatment of the permanent magnet by a sand blasting machine, the diameter of the steel shot in the sand blasting machine is 0.1-0.3 mm, and the blasting time is 10-30 minutes;

Polishing, comprising: polishing the permanent magnet with a polishing device, and polishing time is 20 to 40 minutes;

Cleaning comprises: ultrasonically cleaning the permanent magnet in an organic solvent for 5 to 20 minutes.

In a preferred embodiment, the organic solvent used in the degreasing process includes gasoline, and the lye used includes a NaOH solution having a concentration of 2 mol/l.

In a preferred embodiment, the organic solvent employed in the cleaning process comprises a mixture of absolute ethanol and acetone.

A permanent magnet having a surface having a protective layer formed by any of the foregoing methods for protecting a surface of a magnet.

Further, the permanent magnet is a neodymium iron boron permanent magnet.

In a preferred embodiment, the method for preparing the permanent magnet includes:

The alloy raw material is disposed, and comprises the following components calculated according to the molar percentage content: Nd 23% to 26%, B 0.9% to 0.98%, Co 0.8% to 1.3%, Cu 0.2% to 0.33%, Al 0.14% to 0.2%, Zr 0.2% to 0.6%, and Fe;

The alloy raw material is smelted in a vacuum system, and a quick-setting piece is prepared by a rapid cooling process;

Preparing the quick-setting sheet into a micron-sized alloy magnetic powder by hydrogen fragmentation and jet milling;

And preparing the neodymium iron boron blank by press molding the micron-sized alloy magnetic powder under an inert gas, and then preparing the neodymium iron boron magnet by isostatic pressing and sintering.

More preferably, the quick-setting slab has a thickness of 0.3 to 0.4 mm.

More preferably, the micron-sized alloy magnetic powder has an average particle size of 2.8 to 3.2 μm.

Preferably, the method for preparing the permanent magnet comprises:

After the quick-setting piece is subjected to hydrogen absorbing and crushing treatment, and then charged into a jet mill to prepare the alloy magnetic powder,

The alloy magnetic powder is oriented and formed in a magnetic field of 1600 to 1760 kAm ^-1 , and the green body is molded, followed by cold isostatic pressing, sintering, and tempering.

More preferably, the sintering treatment conditions include a sintering temperature of 1150 to 1200 K and a sintering time of 3 to 5 hours.

More preferably, the tempering treatment conditions include: a first-stage tempering temperature of 1030 to 1090 K, a time of 2 to 4 hours, a secondary tempering temperature of 730 to 850 K, and a time of 3 to 5 hours.

A device comprising the surface modification layer or the permanent magnet.

Advantages of the present invention over the prior art include:

(1) Providing a method capable of effectively improving the performance of a surface modified layer of a material, which is simple in process, easy to control, low in cost, non-polluting, safe and environmentally friendly, and is particularly suitable for various grades and various preparation methods. NdFeB permanent magnets have protective treatment and have broad application prospects in magnetic material protection;

(2) The surface-modified coating formed by the method of the invention has excellent comprehensive performance, for example, the primer layer prepared by pressure coating of the coating liquid can not only form a dense NdFeB matrix protective layer, but also can enhance the film well. The bonding force between the layer and the substrate; the bonding between the zinc-chromium film and the material matrix is improved by the transition of the underlying layer, and the PCT high temperature aging test time exceeds 480 hours, and the modified layer tensile test exceeds 15MPa. Moreover, the film layer is dense and the thickness is controllable. The salt spray experiment time exceeds 720 hours, which is more than 10 times that of the traditional NdFeB magnet protective layer.

detailed description

In view of the many defects of the existing surface modification technology of materials, especially the shortcomings of the existing NdFeB magnet protection methods, the inventors of the present invention have been able to propose the technical solution of the present invention through long-term research and extensive practice, as described above. .

In a more specific embodiment of the present invention, the inventor of the present invention has optimized the main processes of preparation of neodymium iron boron magnets, magnet surface pretreatment, primer precoating treatment, and zinc chromium membrane preparation, thereby developing The surface modification coating of the magnet with excellent comprehensive performance, the zinc-chrome coating formed by the coating has a salt spray resistance of more than 10 times that of the traditional NdFeB magnet protective layer, and the weather resistance and bonding force are also larger than the traditional protective layer. improve.

For example, a method for improving the performance of a surface modification layer of a material of the present invention may include preparation of a matrix permanent magnet material, pretreatment of a permanent magnet material, precoating treatment of a primer layer, ratio of a zinc chromium treatment solution, and a zinc chromium film. The preparation and performance test are used to effectively improve the comprehensive performance of the surface modification layer of the permanent magnet material, and the process is simple, the controllability is good, the yield is high, and it is suitable for large-scale production.

Wherein, the permanent magnet material comprises NdFeB permanent magnets obtained by different brands and preparation methods, and of course other permanent magnet materials, in particular rare earth permanent magnet materials.

The specific embodiment may include: taking high purity Nd, B, Co, Cu, Al, Zr, Fe with a purity greater than 99.9 wt%. A neodymium iron boron magnet prepared by a process such as vacuum melting-speed coagulation-hydrogen crushing-flow milling-forming-isostatic pressing-sintering. The uniform specification sample is prepared by wire cutting and slicing machine, the rust is removed by sandblasting, the scale is removed, the surface of the sample is polished by grinding machine processing, and the surface of the magnet is further cleaned in an ultrasonic environment by a mixture of absolute ethanol and acetone. . The surface-treated magnet is subjected to pre-coating treatment by using the prepared inorganic zinc-rich silica sol, and then the underlying layer is subjected to low-temperature heat treatment, and the heat-treated NdFeB magnet is again subjected to zinc chromium liquid coating, and finally The magnet is heat-treated at a high temperature to obtain a zinc-chromium film excellent in overall performance.

Further, the specific implementation may include:

(1) taking alloy raw materials such as Nd, B, Co, Cu, Al, Zr, Fe, etc.;

(2) melting the alloy raw material in a vacuum system, and preparing a quick-setting piece by a rapid cooling process;

(3) preparing the quick-setting sheet by hydrogen crushing and jet milling to form a micron-sized alloy magnetic powder;

(4) preparing the neodymium iron boron blank by pressing the magnetic powder under the protection of high purity Ar gas, and preparing the sintered neodymium iron boron magnet by isostatic pressing and sintering;

(5) Uniform specification preparation and surface pretreatment of the sintered NdFeB magnet.

(6) Performing primer pre-spraying and low-temperature heat treatment on the pre-treated magnet.

(7) The heat-treated magnet is subjected to zinc chromium liquid coating and high-temperature preheating and solidification treatment.

In a more typical embodiment of the present invention, a method for improving the performance of a surface modification layer of a material may include the following steps:

Step 1) Preparation of NdFeB magnets:

High-purity Nd, B, Co, Cu, Al, Zr, Fe are used as raw materials, and the scale on the surface of the raw material is removed. According to the molar ratio: Nd (23% to 26%), B (0.9% to 0.98%), Co (0.8% to 1.3%), Cu (0.2% to 0.33%), Al (0.14% to 0.2%), Zr (0.2% to 0.6%), and Fe (bal) are formulated as raw materials, of which all components are The sum of the contents is 100%.

5~10kg of raw materials are placed in a vacuum induction melting furnace to prepare alloy quick-setting slabs. The alloy slabs are subjected to hydrogen absorbing and crushing treatment, and then loaded into a jet mill to prepare alloy powders. The alloy powders are subjected to a magnetic field of 1600 to 1760 kAm ^-1 . Orientation molding, and then the molded green body is subjected to cold isostatic pressing treatment, and the green compact sintering furnace is used to sinter the green body and tempering. The size of the sintered magnet finally prepared is 52.5 mm × 52.5 mm × 34.5 mm (length × width × height). The height dimension direction is the direction of the magnetic field orientation during the green molding, and the prepared sintered magnet blank is processed into a cylinder of 10.2 mm (tolerance less than 0.1 mm) in the orientation direction by a wire cutter, and then cut into a height by a microtome. Small cylinder of 10mm (3mm before the front and back of the cylinder are removed before breaking the small cylinder).

Step 2) Magnet surface pretreatment:

The small cylinder prepared in the step 1) is used to remove the oil on the surface by using gasoline and a 2 mol/L NaOH solution, and then placed in a sand blasting machine for surface descaling and descaling treatment, and then the small cylinder is in a cylindrical grinding machine. The surface is polished. Finally, the polished small cylinder is placed in a mixture of absolute ethanol and acetone. The surface of the magnet is further decontaminated under the action of ultrasonic waves. The small cylinder is taken out and air-dried at room temperature, and the surface of the magnet is cleaned. The liquid is evaporated and dried for use.

Step 3) pre-coating treatment: one or more of sodium water glass, potassium water glass or lithium water glass are added to the inorganic gel and mixed well, and then the silane coupling agent is added, and the solution is continuously stirred to make the solution half. In the form of transparent colloid, zinc powder is added to the mixed sol in batches, and the pH value of the mixed sol is adjusted by using a pH adjusting agent. The stirring process is continuously stirred, and then the zinc-rich silica sol is placed in a suction spray gun tank, and the nozzle is sprayed. The diameter is Ф16mm, and the surface-treated magnet is placed on the self-designed mesh bracket, and the magnet is subjected to a mixed-air spraying treatment, and then the magnet and the bracket are placed together in a circulating hot air baking oven for drying.

Step 4) Preparation of zinc-chromium film: Analyze pure zinc flake powder, aluminum powder, chromic anhydride, boric acid, surfactant, pH adjuster, other additives and appropriate amount of deionized water, and mix zinc oxide coating according to a certain ratio. Liquid, the preparation process is continuously stirred by the frequency conversion mixer, so that the zinc chromium coating liquid is thoroughly mixed uniformly without delamination or suspension, and then the zinc chromium coating liquid is loaded into the spraying gun (the same specifications as the spraying gun used in step 3), The pre-coated magnet is coated with zinc chromium solution, and finally the magnet and the holder are placed together in a circulating hot air baking oven for drying.

In the exemplary embodiment, the materials and process conditions used in the respective processes may adopt the preferred materials or conditions listed in the foregoing, and are not described herein again.

The preferred embodiments of the present invention are described in detail below with reference to the preferred embodiments of the present invention.

Example 1

(1) Nd, B, Co, Cu, Al, Zr, Fe raw materials according to the molar percentage Nd 25.8%, B 0.98%, Co1%, Cu 0.27%, Al 0.18%, Zr 0.4%, Febal ratio, total alloy The mass is 5kg, and it is placed in a vacuum induction melting furnace. The charging process is carried out by charging-vacuum-preheating-filling argon-high-power smelting-small power stirring-casting. Cooling, rotation speed is about 35 ~ 50 revolutions per minute) to form a thin crystal with a thickness of about 0.3 ~ 0.4mm, and select an alloy quick-setting sheet with smoothness, uniform thickness and bright color to prepare for powdering.

(2) The selected quick-setting piece is loaded into a special hydrogen crushing furnace, and is tested by positive and negative pressure-hydrogen-heating-vacuum dehydrogenation- Cooling-extrusion and other processes for coarse crushing treatment, the hydrogen powder is placed in a nitrogen-protected glove, and an antioxidant and a surfactant are added and thoroughly stirred, and then charged into a jet abrasive tank to be powdered in a nitrogen atmosphere. The oxygen content of the powder process is controlled below 100 ppm).

(3) sifting the magnetic powder after the jet mill treatment, and selecting the powder with an average particle size of 2.8-3.2 μm into the tank and directly connecting it to the glove box of the automatic pollination system, through the weighing-feeding-magnetizing- Press forming (size: 52.5mm × 52.5mm × 34.5mm (length × width × height), the height dimension direction is the direction of magnetic field orientation during green molding) - demagnetization - pressure release demoulding (density after molding is 4.0 ～4.2g/cm ³ )—Package—Inspection—Cool isostatic pressing (density after completion of isostatic pressing is 4.5 to 4.9 g/cm ³ — cleaning, inspection, etc. to prepare a magnet green body.

(4) The formed blank is placed in a box of a sintering furnace in an argon-protected glove box, and is evacuated by vacuum-washing-vacuum-heating and venting-heating aging (temperature: 1150K, time: 5h) - First-stage tempering (temperature: 1090K, time: 2h) - secondary tempering (temperature: 850, time: 3h) - sintered magnet blank prepared by cooling-out process (magnet density is 7.65 ~ 7.68) g/cm ³ , the crystallite size of the magnet is 3 to 5 μm).

(5) The prepared sintered magnet blank is processed into a cylinder of 10.2 mm (tolerance less than 0.1 mm) in the orientation direction by a wire cutter, and then cut into a cylinder with a height of 15 mm by a slicer. Remove the front and back ends of the long cylinder by 2mm).

(6) The small cylinder after slicing is used to remove the oil stain on the surface with gasoline and a 2 mol/L NaOH solution, and then placed in a sand blasting machine for surface descaling and descaling treatment (steel shot diameter: 0.1~) 0.3mm, sand blasting time: 10 minutes). After that, the small cylinder is surface-polished on a cylindrical grinding machine (polishing time: 20 minutes). Finally, the polished small cylinder is placed in a mixture of absolute ethanol and acetone, and the surface of the magnet is further decontaminated by ultrasonic waves. Treatment (ultrasonic frequency is 100 Hz, cleaning time: 5 minutes), and the small cylinder is taken out and air-dried at room temperature for use.

(7) While cleaning the surface of the magnet, add sodium silicate glass and add zinc silicate to mix well (2% of the total mass of the mixed sol), then add silane coupling agent (silane coupling agent to the total mass) 3%) The mixture was continuously stirred to make the solution semi-transparent colloidal, and the zinc powder having a particle size of 3.2 μm was added to the mixed sol in batches, and the mass ratio of the total amount of the sol to the zinc powder was 1:2. After waiting for the zinc-rich silica sol to stabilize for 10 minutes, the pH of the zinc-rich silica sol was adjusted by 4 with a ZnO pH adjusting agent, and the stirring process was continued to stir, so that the zinc-rich silica sol was a homogeneous solution without delamination and suspension. .

(8) The uniformly mixed zinc-rich silica sol is placed in a suction spray gun tank (2/3 of the volume of the sol container, the nozzle diameter is Ф16 mm), and the surface-treated magnet is placed on the self-designed net. On the bracket, the magnet is sprayed with a mixture (the working distance between the spray gun and the magnet is 10 cm, the pressure of the spray gun is 3 MPa), and then the magnet and the bracket are placed together. Drying in a hot air baking oven, the drying temperature is 40 ° C, and the drying time is 10 minutes.

(9) Preparation of zinc-chromium coating solution: Firstly, pure zinc flake powder and aluminum powder (zinc powder and aluminum powder have a thickness of 0.2 μm, an average particle diameter of 4 μm, and a zinc powder content of 35% (mass percentage, as follows). Unless otherwise specified, the aluminum powder content is 10%) Stir well, add 0.5% surfactant in sequence (the surfactant is a mixture of propylene glycol butyl ether and divinyl alcohol), 25% auxiliary ( The auxiliary agent is a mixture of glycerol and hydroxyethyl cellulose. The preparation process is continuously stirred to uniformly disperse the zinc aluminum paste; then 8% of chromic anhydride, 0.5% boric acid is added continuously and stirred, and then 1.8% of ZnO is added. pH adjuster and appropriate amount of deionized water to adjust the pH and viscosity of the slurry, adjust the pH to 4.5; the mixture to be formed is uniform without delamination, and finally slowly add 2% reducing agent (the reducing agent is succinic acid and The mixture of acrylic acid), the adding process adjusts the stirrer to stir rapidly, so that there is no agglomeration in the mixed liquid, and after the reducing agent is completely added, the stirring is continued for 30 minutes to stabilize the solution to obtain the finished coating liquid.

(10) Put the prepared zinc-chromium coating liquid into the spray gun (the same specifications as the spray gun used in step 8), and apply the zinc-chromium solution to the low-temperature dried magnet. The working interval between the spray gun and the magnet is 15cm, the gun pressure is 2MPa. The temperature of the circulating hot air baking oven is adjusted to 60 ° C. After the temperature is stabilized, the coated magnet and the bracket are placed together in a baking furnace, and the zinc chromium film is preheated and dried for 10 minutes, after which the baking furnace is The temperature was raised to 280 ° C at a rate of 5 ° C / min to cure the zinc chromium film, and the temperature was kept stable for 15 minutes.

(11) After the film is cured, the magnet is cooled to room temperature with the furnace, and the performance of the magnet coating is tested. The experimental conditions are shown in Table 1, and the test results are shown in Table 2.

Table 1 Experimental conditions for testing the performance of the magnet coating used in Example 1

Example 2

Steps (1) to (5) are the same as steps (1) to (5) in Example 1;

The differences are as follows:

(6) The small cylinder after slicing is used to remove the oil stain on the surface with gasoline and a 2 mol/L NaOH solution, and then placed in a sand blasting machine for surface descaling and descaling treatment (steel shot diameter: 0.1~) 0.3mm, sandblasting time: 20 minutes). After that, the small cylinder is surface-polished on a cylindrical grinding machine (polishing time: 30 minutes). Finally, the polished small cylinder is placed in a mixture of absolute ethanol and acetone, and the surface of the magnet is further decontaminated by ultrasonic waves. Treatment (ultrasonic frequency is 100 Hz, cleaning time: 10 minutes), and the small cylinder is taken out and air-dried at room temperature for use.

(7) While cleaning the surface of the magnet, add sodium water glass to the zinc silicate and mix well (6% of the total weight of the mixed sol), then add the silane coupling agent (the silane coupling agent accounts for the total weight). 2%) continuously stirring to make the solution a translucent colloid, and a zinc powder having a particle size of 3.2 μm was added to the mixed sol in batches, and the mass ratio of the sol to the zinc powder was 1:2. After waiting for the zinc-rich silica sol to stabilize for 10 minutes, the pH of the zinc-rich silica sol was adjusted by using a ZnO pH adjusting agent, and the stirring process was continued to stir, so that the zinc-rich silica sol was a homogeneous solution without delamination and suspension.

(8) The uniformly mixed zinc-rich silica sol is placed in a suction spray gun tank (2/3 of the volume of the sol container, the nozzle diameter is Ф16 mm), and the surface-treated magnet is placed on the self-designed net. On the bracket, the magnet is sprayed with a mixture (the working interval between the spray gun and the magnet is 15cm, the pressure of the spray gun is 3MPa), and then the magnet and the bracket are placed together in a circulating hot air baking oven for drying. The drying temperature is 60. °C, drying time is 10 minutes.

(9) Preparation of zinc-chromium coating solution: preparation of zinc-chromium coating solution: firstly, pure zinc flake powder and aluminum powder (the thickness of zinc powder and aluminum powder is 0.2 μm, the average particle diameter is 4 μm, and the zinc powder content is 30%, aluminum powder content is 8%) Stir well, add 0.7% surfactant in sequence (surfactant is a mixture of propylene glycol butyl ether and divinyl alcohol), 20% auxiliary (auxiliary a mixture of glycerol and hydroxyethyl cellulose), the mixing process is continuously stirred to uniformly disperse the zinc aluminum paste; then 6% of chromic anhydride, 0.5% boric acid is added continuously and stirred, and then 1.2% of ZnO pH adjuster is added. Adjust the pH and viscosity of the slurry with a proper amount of deionized water, adjust the pH to 4.5; the mixture to be formed is uniform without delamination, and finally add 1.5% reducing agent slowly (the reducing agent is a mixture of succinic acid and acrylic acid). Liquid), adding process to adjust the stirrer to stir quickly so that there is no agglomeration in the mixture, and after the reducing agent is added completely, continue to stir slowly for 60 minutes to stabilize the solution to obtain the finished coating liquid.

Steps (10) to (11) are the same as steps (10) to (11) in Example 1;

The comprehensive performance of the samples obtained in this example can be seen in Table 2.

Example 3

Steps (1) to (5) are the same as steps (1) to (5) in Example 2;

(6) The small cylinder after slicing is used to remove the oil stain on the surface with gasoline and 2% NaOH solution, and then placed in the sand blasting machine for surface descaling and descaling treatment (steel shot diameter: 0.1-0.3) Mm, sand blasting time: 30 minutes). After that, the small cylinder is surface-polished on the cylindrical grinding machine (polishing time: 40 minutes), and finally the polished small cylinder is placed in a mixture of absolute ethanol and acetone to further decontaminate the surface of the magnet under the action of ultrasonic waves. Treatment (ultrasonic frequency is 100 Hz, cleaning time: 20 minutes), and the small cylinder is taken out and air-dried at room temperature for use.

(7) While cleaning the surface of the magnet, add sodium silicate glass and add zinc silicate to mix well (8% zinc silicate accounts for 8% of the total weight of the mixed sol), and then add silane coupling agent (silane coupling agent to the total weight) 3%) The mixture was continuously stirred to make the solution semi-transparent colloidal. The zinc powder with a particle size of 3.6 μm was added to the mixed sol in batches, and the mass ratio of the sol to the zinc powder was 1:2. After waiting for the zinc-rich silica sol to stabilize for 10 minutes, the pH of the zinc-rich silica sol was adjusted by using a ZnO pH adjusting agent, and the stirring process was continued to stir, so that the zinc-rich silica sol was a homogeneous solution without delamination and suspension.

(8) The uniformly mixed zinc-rich silica sol is placed in a suction spray gun tank (2/3 of the volume of the sol container, the nozzle diameter is Ф16 mm), and the surface-treated magnet is placed on the self-designed net. On the bracket, the magnet is sprayed with a mixture (the working distance between the spray gun and the magnet is 10 cm, and the pressure of the spray gun is 4 MPa). Then, the magnet and the bracket are placed together in a circulating hot air baking oven to dry at a temperature of 60. °C, drying time is 30 minutes.

(9) Preparation of zinc-chromium coating solution: Firstly, pure zinc flake powder and aluminum powder (zinc powder and aluminum powder have a thickness of 0.2 μm, an average particle diameter of 4 μm, a zinc powder content of 25%, and an aluminum powder content of 6%) Stir well, add 0.7% surfactant in sequence (surfactant is a mixture of propylene glycol butyl ether and divinyl alcohol), 18% auxiliary (auxiliary is glycerol and hydroxyethyl cellulose) Mixture), the mixing process is continuously stirred to uniformly disperse the zinc-aluminum paste; then 4% chromic anhydride, 1% boric acid is added in sequence and stirring is continued, followed by adding 1.3% ZnO pH adjuster and appropriate amount of deionized water to adjust the pH of the slurry. And viscosity, adjust the pH value of 5; the mixture to be formed is uniform without delamination, and finally slowly add 1% reducing agent (reducing agent is a mixture of succinic acid and acrylic acid), adding process to adjust the mixer quickly Stirring so that there is no agglomeration in the mixed solution, and after the reducing agent is added completely, stirring is continued for 120 minutes to stabilize the solution to obtain a finished coating liquid.

(10) Put the prepared zinc-chromium coating liquid into the spray gun (the same specifications as the spray gun used in step 8), and apply the zinc-chromium solution to the low-temperature dried magnet. The working interval between the spray gun and the magnet is 20cm, the gun pressure is 4MPa. The temperature of the circulating hot air baking oven is adjusted to 80 ° C. After the temperature is stabilized, the coated magnet and the bracket are placed together in a baking furnace, and the zinc chromium film is preheated and dried for 30 minutes, after which the baking furnace is The temperature of 5 ° C / min is raised to 280 ° C to cure the zinc chromium film. After the temperature was stable, the temperature was kept for 30 minutes.

Step (11) is the same as step (11) in Embodiment 2;

The comprehensive performance of the samples obtained in this example can be seen in Table 2.

Example 4

Steps (1) to (6) are the same as steps (1) to (6) in Example 3;

(7) While cleaning the surface of the magnet, add sodium silicate glass and add zinc silicate to mix well (10% of the total weight of the mixed sol), then add silane coupling agent (silane coupling agent to the total weight) 5%) The mixture was continuously stirred to make the solution a translucent colloid. The zinc powder having a particle size of 3.6 μm was added to the mixed sol in batches, and the mass ratio of the sol to the zinc powder was 1:3. After waiting for the zinc-rich silica sol to stabilize for 10 minutes, the pH of the zinc-rich silica sol was adjusted by using a ZnO pH adjusting agent, and the stirring process was continued to stir, so that the zinc-rich silica sol was a homogeneous solution without delamination and suspension.

Step (8) and step (8) in Embodiment 3;

(9) Preparation of zinc-chromium coating solution: Firstly, pure zinc flake powder and aluminum powder (zinc powder and aluminum powder have a thickness of 0.3 μm, an average particle diameter of 4 μm, a zinc powder content of 25%, and an aluminum powder content of 3%) Stir well, add 1% surfactant in sequence (surfactant is a mixture of propylene glycol butyl ether and divinyl alcohol), 15% auxiliary (auxiliary is glycerol and hydroxyethyl cellulose) Mixture), the mixing process is continuously stirred to uniformly disperse the zinc-aluminum paste; then 2.5% chromic anhydride, 1.5% boric acid is added in sequence and stirring is continued, followed by adding 1% ZnO pH adjuster and appropriate amount of deionized water to adjust the pH of the slurry and Viscosity, adjust the pH value of 6; the mixture to be formed is uniform without delamination, and finally slowly add 0.6% of reducing agent (reducing agent is a mixture of succinic acid and acrylic acid), and the process is adjusted to stir the mixer quickly. After the mixture is completely agglomerated, and the reducing agent is added completely, the stirring is continued for 120 minutes to stabilize the solution to obtain a finished coating liquid.

(10) Put the prepared zinc-chromium coating liquid into the spray gun (the same specifications as the spray gun used in step 8), and apply the zinc-chromium solution to the low-temperature dried magnet. The working interval between the spray gun and the magnet is 20cm, the gun pressure is 4MPa. The temperature of the circulating hot air baking oven is adjusted to 120 ° C. After the temperature is stabilized, the coated magnet and the bracket are placed together in a baking furnace, and the zinc chromium film is preheated and dried for 20 minutes, after which the baking furnace is The zinc chromium film was solidified at a rate of 10 ° C / min to 300 ° C, and the temperature was kept stable for 30 minutes.

Step (11) is the same as step (11) in Embodiment 3;

The comprehensive performance of the samples obtained in this example can be seen in Table 2.

Example 5

Steps (1) to (6) are the same as steps (1) to (6) in Example 4;

(7) While cleaning the surface of the magnet, add sodium silicate glass and add zinc silicate to mix well (10% of the total weight of the mixed sol), then add silane coupling agent (silane coupling agent to the total weight) 5%) The mixture was continuously stirred to make the solution semi-transparent colloidal. The zinc powder with a particle size of 4 μm was added to the mixed sol in batches, and the mass ratio of the sol to the zinc powder was 1:3. After waiting for the zinc-rich silica sol to stabilize for 10 minutes, the pH of the zinc-rich silica sol was adjusted to 5.5 with a ZnO pH adjusting agent, and the stirring process was continuously stirred to make the zinc-rich silica sol a homogeneous solution without delamination and suspension.

(8) The uniformly mixed zinc-rich silica sol is placed in a suction spray gun tank (2/3 of the volume of the sol container, the nozzle diameter is Ф16 mm), and the surface-treated magnet is placed on the self-designed net. On the bracket, the magnet is sprayed with a mixture (the working distance between the spray gun and the magnet is 20cm, and the pressure of the spray gun is 6MPa). Then, the magnet and the bracket are placed together in a circulating hot air baking oven for drying. The drying temperature is 80. °C, drying time is 30 minutes.

(9) Preparation of zinc-chromium coating solution: Firstly, the pure zinc flake powder and aluminum powder (zinc powder and aluminum powder have a thickness of 0.3 μm, an average particle diameter of 6 μm, a zinc powder content of 15%, and an aluminum powder content of 3%) Stir well, add 1% surfactant in sequence (surfactant is a mixture of propylene glycol butyl ether and divinyl alcohol), 10% auxiliary (auxiliaries are glycerol and hydroxyethyl cellulose) Mixture), the mixing process is continuously stirred to uniformly disperse the zinc-aluminum paste; then 2.5% chromic anhydride, 1.5% boric acid is added in sequence and stirring is continued, followed by adding 1% ZnO pH adjuster and appropriate amount of deionized water to adjust the pH of the slurry and Viscosity, adjust the pH value of 5; the mixture to be formed is uniform without delamination, and finally slowly add 0.6% of reducing agent (reducing agent is a mixture of succinic acid and acrylic acid), and the process is adjusted to stir the mixer quickly. After the mixture is completely agglomerated, and the reducing agent is added completely, the stirring is continued for 120 minutes to stabilize the solution to obtain a finished coating liquid.

(10) Put the prepared zinc-chromium coating liquid into the spray gun (the same specifications as the spray gun used in step 8), and apply the zinc-chromium solution to the low-temperature dried magnet. The working interval between the spray gun and the magnet is 15cm, the gun pressure is 4MPa. The temperature of the circulating hot air baking oven is adjusted to 100 ° C. After the temperature is stabilized, the coated magnet and the bracket are placed together in a baking furnace, and the zinc chromium film is preheated and dried for 20 minutes, after which the baking furnace is The temperature was raised to 300 ° C at a rate of 20 ° C / min to cure the zinc chromium film, and the temperature was kept stable for 20 minutes.

Step (11) is the same as step (11) in Embodiment 4;

The comprehensive performance of the samples obtained in this example can be seen in Table 2.

Example 6

Steps (1) to (3) are the same as steps (1) to (3) in Example 5;

(4) The formed blank is placed in a box of a sintering furnace in an argon-protected glove box, and is evacuated by vacuum-washing-vacuum-heating and venting-heating aging (temperature: 1200 K, time: 3 h) - First-stage tempering (temperature: 1030K, time: 4h) - secondary tempering (temperature: 730, time: 5h) - sintered magnet blank prepared by cooling-out process (magnet density is 7.60 ~ 7.63 g/cm ³ , the crystal grain size of the magnet is 5 to 10 μm);

Steps (5) to (6) are the same as steps (5) to (6) in Example 5;

Step (7) is the same as step (7) in Embodiment 2;

(8) The uniformly mixed zinc-rich silica sol is placed in a suction spray gun tank (2/3 of the volume of the sol container, the nozzle diameter is Ф16 mm), and the surface-treated magnet is placed on the self-designed net. On the bracket, the magnet is sprayed with a mixture (the working interval between the spray gun and the magnet is 15cm, the pressure of the spray gun is 6MPa), and then the magnet and the bracket are placed together in a circulating hot air baking oven for drying. The drying temperature is 80. °C, drying time is 30 minutes.

(9) Preparation of zinc-chromium coating solution: Firstly, pure zinc flake powder and aluminum powder (zinc powder and aluminum powder have a thickness of 0.3 μm, an average particle diameter of 4 μm, a zinc powder content of 20%, and an aluminum powder content of 3%) Stir well, add 1% surfactant in sequence (surfactant is a mixture of propylene glycol butyl ether and divinyl alcohol), 18% auxiliary (auxiliary is glycerol and hydroxyethyl cellulose) Mixture), the mixing process is continuously stirred to uniformly disperse the zinc-aluminum paste; then 3% of chromic anhydride, 1.5% boric acid is added in sequence and stirring is continued, followed by adding 1.4% ZnO pH adjuster and appropriate amount of deionized water to adjust the pH of the slurry and Viscosity, adjust the pH value of 6; the mixture to be formed is uniform without delamination, and finally add 1.1% of the reducing agent (the reducing agent is a mixture of succinic acid and acrylic acid), and the process is adjusted to stir the mixer quickly. After the mixture is completely agglomerated, and the reducing agent is added completely, the stirring is continued for 120 minutes to stabilize the solution to obtain a finished coating liquid.

(10) Put the prepared zinc-chromium coating liquid into the spray gun (the same specifications as the spray gun used in step 8), and apply the zinc-chromium solution to the low-temperature dried magnet. The working interval between the spray gun and the magnet is 15cm, the gun pressure is 4MPa. The temperature of the circulating hot air baking oven is adjusted to 100 ° C. After the temperature is stabilized, the coated magnet and the bracket are placed together in a baking furnace, and the zinc chromium film is preheated and dried for 20 minutes, after which the baking furnace is The temperature is raised to 300 ° C at a rate of 5 ° C / min to cure the zinc chromium film, and the temperature is kept stable for 20 minutes;

Step (11) is the same as step (11) in Embodiment 5;

The comprehensive performance of the samples obtained in this example can be seen in Table 2.

Comparative example 1

Steps (1) to (6) are the same as steps (1) to (6) in Example 5;

Step (7) is the same as step (9) in Example 3, to prepare a single-layer zinc-chromium film;

Steps (8) to (9) are the same as steps (10) to (11) in Example 6;

The comprehensive performance of the samples obtained in this example can be seen in Table 2.

Comparative example 2

Steps (1) to (8) are the same as steps (1) to (8) in Comparative Example 1;

Steps (9) to (10) repeat steps (7) to (8) to prepare a double-layer zinc-chromium film;

Step (11) is the same as step (11) in Comparative Example 1;

The comprehensive performance of the samples obtained in this example can be seen in Table 2.

Comparative example 3

Steps (1) to (8) are the same as steps (1) to (8) in Example 3, and a zinc-rich film is prepared;

Step (9) is the same as step (9) in Comparative Example 1;

The comprehensive performance of the samples obtained in this example can be seen in Table 2.

Comparative example 4

Steps (1) to (5) are the same as steps (1) to (5) in Example 5;

Step (6) preparing the small cylinder after slicing by (baking)→grinding→cleaning→sealing→polishing→deoiling→water washing→lighting→water washing→activation (preplating)→electroplating→cold water washing→drying Zinc plating (plating solution formulation and plating process parameters using traditional electroplating process);

Step (7) is the same as step (11) in Embodiment 6;

The comprehensive performance of the samples obtained in this example can be seen in Table 2.

Comparative example 5

Steps (1) to (5) are the same as steps (1) to (5) in Example 5;

Step (6) preparing the small cylinder after slicing by (baking)→grinding→cleaning→sealing→polishing→deoiling→water washing→lighting→water washing→activation (preplating)→electroplating→cold water washing→drying Nickel-copper-nickel plating (plating solution formulation and plating process parameters using traditional electroplated nickel-copper-nickel process);

Step (7) is the same as step (11) in Embodiment 6;

The comprehensive performance of the samples obtained in this example can be seen in Table 2.

Table 2 Results of comprehensive performance test of Examples 1 to 6 and Comparative Examples 1 to 3

It is to be understood that the term "comprises", "comprising" or any other variations thereof is intended to encompass a non-exclusive inclusion, such that a process, method, article, or device that comprises a It also includes other elements that are not explicitly listed, or elements that are inherent to such a process, method, item, or device.

It should be noted that the above description is only a specific embodiment of the present invention, and those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It should be considered as the scope of protection of the present invention.

Claims (23)

1. A method for improving the performance of a surface modification layer of a material, comprising:

   Applying an inorganic zinc-rich silica sol to the surface of the material to be treated to form a primer layer,

   And coating a zinc chromium coating solution on the primer layer to form a zinc chromium film;

   The inorganic zinc-rich silica sol comprises a soluble alkali metal silicate material, an inorganic gel and an ultrafine zinc powder.

   The zinc chromium coating liquid includes flake zinc powder, aluminum powder, chromic anhydride, boric acid, a surfactant, a pH adjuster, and deionized water.
2. The method for improving the performance of a surface modification layer of a material according to claim 1, wherein the preparation process of the inorganic zinc-rich silica sol comprises: mixing an inorganic gel with a soluble alkali metal silicate material, and then adding a silane The coupling agent and the pH adjuster control the pH of the mixed solution to 4 to 5.5 while continuously stirring until the mixed solution is in the form of a translucent colloid, and then adding the ultrafine zinc powder.
3. The method for improving the properties of a surface modification layer of a material according to claim 1 or 2, wherein:

   The soluble alkali metal silicate material comprises any one or a combination of two or more of sodium water glass, potassium water glass and lithium water glass;

   And/or, the pH adjusting agent comprises ZnO and/or CaO.
4. The method for improving the properties of a surface modification layer of a material according to claim 1 or 2, wherein the inorganic zinc-rich silica sol comprises 2 to 10% by weight of an inorganic gel, and the inorganic gel comprises potassium silicate and/or Zinc silicate.
5. The method for improving the properties of a surface modification layer of a material according to claim 1 or 2, wherein the inorganic zinc-rich silica sol further comprises 0.8 to 5 wt% of an auxiliary agent, and the auxiliary agent comprises a silane coupling agent.
6. The method for improving the performance of a surface modification layer of a material according to claim 1 or 2, wherein the mass ratio of the total amount of the inorganic zinc-rich silica sol to the ultrafine zinc powder is 1:2 to 4, the ultrafine The zinc powder has a particle size of 3.2 to 4 μm.
7. The method for improving the properties of a surface modification layer of a material according to claim 1, wherein the zinc chromium coating solution comprises 15 to 35 wt% of flake zinc powder, 3 to 10 wt% of aluminum powder, and 2.5 to 8 wt% of chromic anhydride. 0.5 to 1.5 wt% of boric acid, 0.5 to 1 wt% of a surfactant, 0.6 to 2 wt% of a reducing agent, 1 to 1.8 wt% of a pH adjuster, and 10 to 25 wt% of an auxiliary agent.
8. The method for improving the performance of a surface modification layer of a material according to claim 7, wherein the preparation method of the zinc chromium coating liquid comprises: firstly dispersing zinc powder, aluminum powder, surfactant and auxiliary agent to form a uniform dispersion. The zinc-aluminum slurry is added with chromic anhydride and boric acid in sequence, and stirring is continued. Next, a pH adjuster and deionized water are added to adjust the pH and viscosity of the slurry. After the mixture to be formed is uniformly layered, the reducing agent is slowly added. Moreover, the stirring speed needs to be increased during the addition process, and after the reducing agent is added completely, the stirring is continued for 30 minutes or more to stabilize the formed mixture.
9. A method of improving the properties of a surface modification layer of a material according to claim 1, 7 or 8, characterized in that:

   The surfactant includes any one of polyoxyethylene nonyl phenol and divinyl alcohol or a combination of two or more;

   And/or, the reducing agent includes any one or a combination of two or more of succinic acid, acrylic acid, and fatty acid;

   And/or, the adjuvant comprises glycerol and/or hydroxyethylcellulose.
10. A method of improving the properties of a surface modification layer of a material according to claim 1, 7 or 8, characterized in that:

    The flake zinc powder is an analytically pure zinc powder having a thickness of 0.2 to 0.3 μm and an average particle diameter of 4 to 6 μm;

    And/or, the aluminum powder is a sheet-like analytical pure aluminum powder having a thickness of 0.2 to 0.3 μm and an average particle diameter of 4 to 6 μm.
11. The method for improving the properties of a surface modification layer of a material according to claim 1, 7 or 8, wherein the zinc chromium coating solution has a pH of 4.5 to 6.
12. The method for improving the properties of a surface modification layer of a material according to claim 1, comprising:

    Spraying the inorganic zinc-rich silica sol onto the surface of the material to be treated by a spray gun to form a primer layer, wherein the pressure of the spray gun is 3-6 MPa, and the working interval between the spray gun and the magnet is 10-20 cm;

    And drying the bottom layer, wherein the drying temperature is 40 to 80 ° C, the drying time is 10 to 30 minutes, and then the zinc chromium coating liquid is applied.
13. The method for improving the properties of a surface modification layer of a material according to claim 1 or 12, comprising:

    Spraying the zinc-chromium coating liquid on the primer layer by a spray gun to form a coating layer, wherein the pressure of the spray gun is 2 to 4 MPa, and the working interval between the spray gun and the magnet is 15 to 20 cm;

    And preheating and drying the coating, wherein the preheating drying treatment temperature is 60 to 120 ° C, the time is 10 to 30 minutes, and then curing treatment is performed, the curing temperature is 280 to 300 ° C, and the processing time is 15 ~40 minutes.
14. The method for improving the performance of a surface modification layer of a material according to claim 13, comprising: raising the temperature to a curing temperature at a temperature increase rate of 5 ° C to 20 ° C / min after the preheating drying treatment is completed, and Curing treatment is carried out.
15. The method for improving the performance of a surface modification layer of a material according to claim 1 or 12, comprising: pretreating the surface of the material to be treated, and then coating an inorganic zinc-rich silica sol on the surface of the material to be treated; Treatment includes degreasing, descaling, polishing and cleaning.
16. A surface modified layer produced by the method of any one of claims 1-15.
17. A method for protecting a surface of a magnet, comprising:

    Providing a magnet and pretreating the surface of the magnet;

    And forming a protective layer on the surface of the magnet by the method of any one of claims 1-15.
18. The method of protecting a surface of a magnet according to claim 17, wherein said magnet comprises a neodymium iron boron permanent magnet having a crystal grain size of 3 to 10 μm.
19. The method of protecting a surface of a magnet according to claim 17, wherein said pre-processing comprises:

    Degreasing, comprising: removing oil stain on the surface of the permanent magnet with an organic solvent and/or an alkali solution;

    Derusting, including: surface rust removal and descaling treatment of the permanent magnet by a sand blasting machine, the diameter of the steel shot in the sand blasting machine is 0.1-0.3 mm, and the blasting time is 10-30 minutes;

    Polishing, comprising: polishing the permanent magnet with a polishing device, and polishing time is 20 to 40 minutes;

    Cleaning comprises: ultrasonically cleaning the permanent magnet in an organic solvent for 5 to 20 minutes.
20. A permanent magnet, characterized in that the surface of the permanent magnet has a protective layer formed by the method of any one of claims 17-19.
21. The permanent magnet according to claim 20, wherein the permanent magnet is a neodymium iron boron permanent magnet prepared by the following method, the method comprising:

    The alloy raw material is disposed, and comprises the following components calculated according to the molar percentage content: Nd 23% to 26%, B 0.9% to 0.98%, Co 0.8% to 1.3%, Cu 0.2% to 0.33%, Al 0.14% to 0.2%, Zr 0.2% to 0.6%, and Fe;

    The alloy raw material is smelted in a vacuum system, and a quick-setting piece having a thickness of 0.3 to 0.4 mm is prepared by a rapid cooling process;

    The quick-setting sheet is prepared by hydrogen crushing and jet milling to obtain a micron-sized alloy magnetic powder having an average particle size of 2.8-3.2 μm;

    And preparing the neodymium iron boron blank by press molding the micron-sized alloy magnetic powder under an inert gas, and then preparing the neodymium iron boron magnet by isostatic pressing and sintering.
22. The permanent magnet according to claim 21, wherein the method for preparing the neodymium iron boron permanent magnet comprises:

    After the quick-setting piece is subjected to hydrogen absorbing and crushing treatment, and then charged into a jet mill to prepare the alloy magnetic powder,

    The alloy magnetic powder is oriented and formed in a magnetic field of 1600 to 1760 kAm ^-1 , and the green body is molded, and then subjected to cold isostatic pressing treatment, sintering and tempering;

    Wherein the sintering treatment conditions include: a sintering temperature of 1150 to 1200 K, and a sintering time of 3 to 5 hours;

    The conditions of the tempering treatment include: a first-stage tempering temperature of 1030 to 1090 K, a time of 2 to 4 hours, a secondary tempering temperature of 730 to 850 K, and a time of 3 to 5 hours.
23. A device comprising the surface modification layer of claim 16 or the permanent magnet of any one of claims 20-22.