Magnet with magnetic isolation layer and preparation method thereof

Abstract

The invention relates to the technical field of magnets, in particular to a magnet with a magnetic isolation layer and a preparation method thereof.The magnet is obtained after a magnet blank with the surface compounded with the magnetic isolation layer is subjected to heat treatment; the magnet blank comprises the following raw materials: a light and heavy rare earth mixture, ferrite magnetic powder, neodymium iron boron magnet, an antioxidant, an adhesive and high-melting-point carbide. According to the rare earth magnet, the use of heavy rare earth elements is reduced, even the coercive force and residual magnetism of a magnet material can still be remarkably provided under the condition that the heavy rare earth elements are not added, the coercive force and the working temperature of the magnet are further improved by adding the high-melting-point carbide, the magnet with high thermal stability can be prepared, and the service life of the magnet is prolonged. The preparation cost of the magnet is greatly reduced; the method for preparing the magnet is simple and convenient to operate and control, the produced product is high in quality and low in cost, industrial production is facilitated, and meanwhile the defects existing in a previous rare earth magnet can be effectively overcome.

Description

Technical Field

[0001] The invention relates to the technical field of magnets, and in particular to a magnet with a magnetic isolation layer and a preparation method thereof. Background Art

[0002] Magnets are substances that can generate magnetic fields and have the property of attracting ferromagnetic materials such as iron, nickel, cobalt and other metals. Magnets are generally divided into permanent magnets and soft magnets. The materials used as magnetic conductors and electromagnets are mostly soft magnets, and their polarity changes with the polarity of the applied magnetic field; while permanent magnets are hard magnets, which can maintain their magnetism for a long time and are not easy to lose magnetism or be magnetized. Therefore, whether in industrial production or in daily life, hard magnets are one of the most commonly used strong materials. However, the Curie temperature of NdFeB magnets is relatively low, and as the working temperature of the casting increases, its magnetism will weaken. In order to change this characteristic of NdFeB magnets, the existing technology increases the coercive force of NdFeB magnets by adding dysprosium (Dy) and terbium (Tb) to improve its thermal stability and magnetism at high temperatures. However, Dy, Tb, etc. are expensive, and the domestic reserves of heavy rare earths are also on a downward trend. Reducing the use of heavy rare earths to prepare high-energy NdFeB permanent magnets has become one of the key development directions in the future. Summary of the invention

[0003] In order to overcome the shortcomings and deficiencies in the prior art, the purpose of the present invention is to provide a magnet with a magnetic isolation layer. The rare earth magnet can significantly provide the coercive force and remanence of the magnet material while reducing the use of heavy rare earth elements or even without adding heavy rare earth elements. The addition of high melting point carbides further improves the coercive force and operating temperature of the magnet, which is conducive to the preparation of magnets with high thermal stability and greatly reduces the cost of magnet preparation.

[0004] The purpose of the present invention is to provide a method for preparing a magnet with a magnetic isolation layer. The preparation method is simple, easy to operate and control, has high product quality, low cost, is conducive to industrial production, and can effectively overcome the shortcomings of previous rare earth magnets.

[0005] The object of the present invention is achieved through the following technical scheme: a magnet with a magnetic isolation layer, the magnet is obtained by heat treating a magnet blank with a magnetic isolation layer on the surface; the material of the magnetic isolation layer is at least one of Bomal alloy, silicon steel, silicon steel, and soft iron; the magnet blank includes the following raw materials: a mixture of light and heavy rare earths, ferrite magnetic powder, neodymium iron boron magnet, an antioxidant, an adhesive and a high melting point carbide.

[0006] Preferably, the magnet blank comprises the following raw materials in parts by weight: 10-20 parts of light and heavy rare earth mixture, 70-100 parts of ferrite powder, 30-50 parts of neodymium iron boron magnet, 1-5 parts of antioxidant, 6-10 parts of adhesive and 4-8 parts of high melting point carbide.

[0007] The rare earth magnet of the present invention can significantly provide the coercive force and remanence of the magnetic material without adding heavy rare earth elements, and the addition of high melting point carbides further improves the coercive force and working temperature of the magnet, which is conducive to the preparation of magnets with high thermal stability and greatly reduces the cost of magnet preparation. By compounding ferrite magnetic powder and neodymium iron boron magnetic powder, the comprehensive magnetic properties of the magnet are improved, and the manufacturing cost is reduced at the same time. The prepared magnet has good performance and high cost performance.

[0008] Preferably, the light and heavy rare earth mixture comprises 40-60 parts of light rare earth, 10-15 parts of heavy rare earth and 3-7 parts of M.

[0009] Preferably, the light rare earth is at least one of La, Ce, Pr and Nd.

[0010] Preferably, the heavy rare earth is at least one of Tb, Dy, Tm and Y.

[0011] Preferably, M is at least one of Al, Cu, Co, Ni, Zr and Nb.

[0012] The light and heavy rare earth mixture in the present invention is composed of the above raw materials. The light rare earth and heavy rare earth are combined with other metal elements to obtain the light and heavy rare earth mixture RLxRHyMz. The mixture is used in NdFeB magnets, so that the coercive force of the magnet is significantly improved, while ensuring that the original remanence and maximum magnetic energy product of the magnet are not significantly reduced. The use of light rare earth also saves costs. By using the magnet of the light and heavy rare earth mixture, the coercive force of the magnet can be increased by up to about 45%, while the remanence and maximum magnetic energy product remain basically stable.

[0013] Preferably, the ferrite magnetic powder is one or more of strontium ferrite, barium ferrite, lead ferrite and steel ferrite magnetic powder.

[0014] Preferably, the high melting point carbide is at least one of titanium carbide, zirconium carbide, chromium carbide, niobium carbide, tantalum carbide, molybdenum carbide, tungsten carbide, vanadium carbide and hafnium carbide.

[0015] The high melting point carbide used in the present invention can further improve the coercive force and working temperature of the magnet, which is conducive to preparing a magnet with high thermal stability and greatly reduces the cost of magnet preparation.

[0016] Preferably, the binder is polyvinyl alcohol powder, and the particle size of the polyvinyl alcohol powder is 1.0-2.0 μm; the antioxidant is magnesium stearate and / or tributyl borate.

[0017] The present invention also provides a method for preparing a magnet having a magnetic isolation layer, comprising the following steps: S1. According to parts by weight, a mixture of light and heavy rare earths is melted and then crushed to obtain a mixed rare earth alloy powder for later use; S2, according to weight parts, ferrite magnetic powder, NdFeB magnet and high melting point carbide are mixed, and then smelted under the protection of argon gas, and the molten material is rapidly solidified during smelting to obtain a main phase alloy casting sheet for standby use; S3, hydrogen-crushing the main phase alloy flakes to obtain main phase powders, adding the mixed rare earth alloy powders, antioxidants and binders to the main phase powders, mixing them well, and then crushing them into powders of 2.5-3.5 μm by jet milling for later use; S4, placing the powder obtained in step S3 in a magnetic field with a magnetic field strength of 1.5-3.5T under the protection of an inert gas for orientation and shaping, and then subjecting the powder to static pressing at a pressure of 600-800MPa to obtain a magnet blank for standby use; S5, sintering the magnet blank at 1000-1100°C for 5-9h with a heating rate of 8-12°C / min, and then subjecting the magnet blank to primary and secondary tempering to obtain a magnet for standby use; S6, preheating the surface of the magnet obtained in step S5 to 170-200° C., then spraying the magnetic isolation layer particles on the surface of the preheated magnet by plasma spraying to obtain a magnetic isolation coating, and finally obtaining a magnet with a magnetic isolation layer.

[0018] The rare earth magnet in the present invention is obtained by the above-mentioned method, and the rare earth magnet obtained by the above-mentioned method has good coercive force and remanence. The addition of high melting point carbide further improves the coercive force and working temperature of the magnet, which is conducive to the preparation of magnets with high thermal stability and greatly reduces the cost of magnet preparation. The preparation method is simple, easy to operate and control, the product quality is high, the cost is low, it is conducive to industrial production, and at the same time it can effectively overcome the shortcomings of previous rare earth magnets.

[0019] The beneficial effects of the present invention are as follows: the rare earth magnet of the present invention can significantly provide the coercive force and remanence of the magnet material while reducing the use of heavy rare earth elements, or even without adding heavy rare earth elements; the addition of high melting point carbides further improves the coercive force and operating temperature of the magnet, which is conducive to the preparation of magnets with high thermal stability and greatly reduces the cost of magnet preparation.

[0020] The preparation method of the magnet with a magnetic isolation layer of the present invention is simple, the operation and control are convenient, the product quality is high, the cost is low, it is conducive to industrial production, and at the same time, the shortcomings of the previous rare earth magnets can be effectively overcome. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0022] A magnet with a magnetic isolation layer is obtained by heat treating a magnet blank with a magnetic isolation layer on its surface; the material of the magnetic isolation layer is a Bomal alloy; the magnet blank comprises the following raw materials: a mixture of light and heavy rare earths, ferrite magnetic powder, neodymium iron boron magnets, an antioxidant, an adhesive and a high melting point carbide.

[0023] The magnet blank comprises the following raw materials in parts by weight: 10 parts of a mixture of light and heavy rare earths, 70 parts of ferrite magnetic powder, 30 parts of neodymium iron boron magnets, 1 part of an antioxidant, 6 parts of an adhesive and 4 parts of a high melting point carbide.

[0024] The light and heavy rare earth mixture comprises 40 parts of light rare earth, 10 parts of heavy rare earth and 3 parts of M.

[0025] The light rare earth is La; the heavy rare earth is Tb; and M is Al.

[0026] The ferrite magnetic powder is strontium ferrite.

[0027] The high melting point carbide is titanium carbide.

[0028] The adhesive is polyvinyl alcohol powder, and the particle size of the polyvinyl alcohol powder is 1.0 μm; the antioxidant is magnesium stearate.

[0029] The magnet with the magnetic isolation layer is prepared by the following method: S1. According to parts by weight, a mixture of light and heavy rare earths is melted and then crushed to obtain a mixed rare earth alloy powder for later use; S2, according to weight parts, ferrite magnetic powder, NdFeB magnet and high melting point carbide are mixed, and then smelted under the protection of argon gas, and the molten material is rapidly solidified during smelting to obtain a main phase alloy casting sheet for standby use; S3, hydrogen-crushing the main phase alloy flakes to obtain main phase powders, adding the mixed rare earth alloy powders, antioxidants and binders to the main phase powders, mixing them well, and then grinding them into powders of 2.5 μm by jet milling for later use; S4, placing the powder obtained in step S3 in a magnetic field with a magnetic field strength of 1.5T under the protection of an inert gas for orientation and shaping, and then subjecting the powder to static pressing at a pressure of 600MPa to obtain a magnet blank for standby use; S5, sintering the magnet blank at 1000°C for 9h with a heating rate of 8°C / min, and then subjecting the magnet blank to primary and secondary tempering to obtain a magnet for standby use; S6, preheating the surface of the magnet obtained in step S5 to 170°C, and then spraying the magnetic isolation layer particles on the surface of the preheated magnet by plasma spraying to obtain a magnetic isolation coating, and finally obtaining a magnet with a magnetic isolation layer.

[0030] A magnet with a magnetic isolation layer is obtained by heat treating a magnet blank with a magnetic isolation layer on its surface; the material of the magnetic isolation layer is a bomal alloy and silicon steel in a weight ratio of 1:1; the magnet blank comprises the following raw materials: a mixture of light and heavy rare earths, ferrite magnetic powder, neodymium iron boron magnet, an antioxidant, an adhesive and a high melting point carbide.

[0031] The magnet blank comprises the following raw materials in parts by weight: 15 parts of a mixture of light and heavy rare earths, 85 parts of ferrite magnetic powder, 40 parts of neodymium iron boron magnets, 3 parts of an antioxidant, 8 parts of a binder and 6 parts of a high melting point carbide.

[0032] The light and heavy rare earth mixture comprises 50 parts of light rare earth, 12 parts of heavy rare earth and 5 parts of M.

[0033] The light rare earth is composed of La, Ce and Pr in a weight ratio of 0.8:0.7:0.5.

[0034] The heavy rare earth is composed of Tb, Dy and Y in a weight ratio of 0.5:0.7:0.8.

[0035] The M is composed of Al, Cu, Co and Nb in a weight ratio of 0.5:0.7:0.6:0.9.

[0036] The ferrite magnetic powder is composed of strontium ferrite, barium ferrite and steel ferrite magnetic powder in a weight ratio of 0.8:0.7:0.9.

[0037] The high melting point carbide is composed of titanium carbide, zirconium carbide and chromium carbide in a weight ratio of 0.6:0.7:0.5.

[0038] The adhesive is polyvinyl alcohol powder, and the particle size of the polyvinyl alcohol powder is 1.0-2.0 μm; the antioxidant is composed of magnesium stearate and tributyl borate in a weight ratio of 0.5:0.8.

[0039] The magnet with the magnetic isolation layer is prepared by the following method: S1. According to parts by weight, a mixture of light and heavy rare earths is melted and then crushed to obtain a mixed rare earth alloy powder for later use; S2, according to weight parts, ferrite magnetic powder, NdFeB magnet and high melting point carbide are mixed, and then smelted under the protection of argon gas, and the molten material is rapidly solidified during smelting to obtain a main phase alloy casting sheet for standby use; S3, hydrogen-crushing the main phase alloy flakes to obtain main phase powders, adding the mixed rare earth alloy powders, antioxidants and binders to the main phase powders, mixing them well, and then grinding them into 3 μm powders by jet milling for later use; S4, placing the powder obtained in step S3 in a magnetic field with a magnetic field strength of 2.5T under the protection of an inert gas for orientation and shaping, and then subjecting the powder to static pressing at a pressure of 700MPa to obtain a magnet blank for standby use; S5, sintering the magnet blank at 1050°C for 7h with a heating rate of 10°C / min, and then subjecting the magnet blank to primary and secondary tempering to obtain a magnet for standby use; S6, preheating the surface of the magnet obtained in step S5 to 185°C, and then spraying the magnetic isolation layer particles on the surface of the preheated magnet by plasma spraying to obtain a magnetic isolation coating, and finally obtaining a magnet with a magnetic isolation layer.

[0040] A magnet with a magnetic isolation layer is obtained by heat treating a magnet blank with a magnetic isolation layer on its surface; the material of the magnetic isolation layer is soft iron; the magnet blank comprises the following raw materials: a mixture of light and heavy rare earths, ferrite magnetic powder, neodymium iron boron magnets, an antioxidant, an adhesive and a high melting point carbide.

[0041] The magnet blank comprises the following raw materials in parts by weight: 20 parts of a mixture of light and heavy rare earths, 100 parts of ferrite magnetic powder, 50 parts of neodymium iron boron magnets, 5 parts of an antioxidant, 10 parts of a binder and 8 parts of a high melting point carbide.

[0042] The light and heavy rare earth mixture comprises 60 parts of light rare earth, 15 parts of heavy rare earth and 7 parts of M.

[0043] The light rare earth is Ce; the heavy rare earth is Dy; and M is Cu.

[0044] The ferrite magnetic powder is barium ferrite.

[0045] The high melting point carbide is chromium carbide.

[0046] The adhesive is polyvinyl alcohol powder, and the particle size of the polyvinyl alcohol powder is 2.0 μm; the antioxidant is tributyl borate.

[0047] The magnet with the magnetic isolation layer is prepared by the following method: S1. According to parts by weight, a mixture of light and heavy rare earths is melted and then crushed to obtain a mixed rare earth alloy powder for later use; S2, according to weight parts, ferrite magnetic powder, NdFeB magnet and high melting point carbide are mixed, and then smelted under the protection of argon gas, and the molten material is rapidly solidified during smelting to obtain a main phase alloy casting sheet for standby use; S3, hydrogen-crushing the main phase alloy flakes to obtain main phase powders, adding the mixed rare earth alloy powders, antioxidants and binders to the main phase powders, mixing them well, and then grinding them into powders of 3.5 μm by jet milling for later use; S4, placing the powder obtained in step S3 in a magnetic field with a magnetic field strength of 3.5T under the protection of an inert gas for orientation and shaping, and then subjecting the powder to static pressing at a pressure of 800MPa to obtain a magnet blank for standby use; S5, sintering the magnet blank at 1100°C for 5h with a heating rate of 12°C / min, and then subjecting the magnet blank to primary and secondary tempering to obtain a magnet for standby use; S6, preheating the surface of the magnet obtained in step S5 to 200°C, and then spraying the magnetic isolation layer particles on the surface of the preheated magnet by plasma spraying to obtain a magnetic isolation coating, and finally obtaining a magnet with a magnetic isolation layer.

[0048] Comparative Example 1 The difference between this comparative example and the above-mentioned Example 2 is that in this comparative example, no light and heavy rare earth mixture is added to the raw materials of the rare earth magnet. The rest of the contents of this comparative example are the same as those of Example 2, and will not be repeated here.

[0049] Comparative Example 2 The difference between this comparative example and the above-mentioned Example 2 is that in this comparative example, no high melting point carbide is added to the raw material of the rare earth magnet. The rest of the contents of this comparative example are the same as those of Example 2 and will not be repeated here.

[0050] The rare earth magnets obtained in Example 2 and Comparative Example 1-2 were made into cylindrical magnets with a height of Φ250 mm×25 mm, and the maximum magnetic energy product was measured according to GB / T13560-2017. The results are shown in Table 1: Table 1 project Maximum magnetic energy product (MGoe) Remanence / kGs Intrinsic coercivity / kOe Example 2 65 13.69 34.2 Comparative Example 1 62 11.37 31.5 Comparative Example 2 60 13.15 29.7 It can be seen from the data in the table that the rare earth magnet prepared in Example 2 of the present invention has very good maximum magnetic energy product, remanence and intrinsic coercive force. By adding a mixture of light and heavy rare earths and high melting point carbides, the comprehensive magnetic properties of the magnet are improved, while the manufacturing cost is reduced. The prepared magnet has good performance and high cost performance, and can meet more occasions.

[0051] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A magnet having a magnetic isolation layer, characterized in that: The magnet is obtained by heat treating a magnet blank with a magnetic isolation layer on the surface; the magnet blank comprises the following raw materials: a mixture of light and heavy rare earths, ferrite magnetic powder, NdFeB magnets, antioxidants, adhesives and high melting point carbides.

2. A magnet with a magnetic isolation layer according to claim 1, characterized in that: The magnet blank comprises the following raw materials in parts by weight: 10-20 parts of light and heavy rare earth mixture, 70-100 parts of ferrite magnetic powder, 30-50 parts of neodymium iron boron magnet, 1-5 parts of antioxidant, 6-10 parts of adhesive and 4-8 parts of high melting point carbide.

3. The magnet with a magnetic isolation layer according to claim 1, characterized in that: The light and heavy rare earth mixture comprises 40-60 parts of light rare earth, 10-15 parts of heavy rare earth and 3-7 parts of M.

4. The magnet with a magnetic isolation layer according to claim 3, characterized in that: The light rare earth is at least one of La, Ce, Pr and Nd; the heavy rare earth is at least one of Tb, Dy, Tm and Y.

5. The magnet with a magnetic isolation layer according to claim 3, characterized in that: The M is at least one of Al, Cu, Co, Ni, Zr and Nb.

6. The magnet with a magnetic isolation layer according to claim 1, characterized in that: The ferrite magnetic powder is one or more of strontium ferrite, barium ferrite, lead ferrite and steel ferrite magnetic powder.

7. The magnet with a magnetic isolation layer according to claim 1, characterized in that: The high melting point carbide is at least one of titanium carbide, zirconium carbide, chromium carbide, niobium carbide, tantalum carbide, molybdenum carbide, tungsten carbide, vanadium carbide and hafnium carbide.

8. The magnet with a magnetic isolation layer according to claim 1, characterized in that: The adhesive is polyvinyl alcohol powder, and the particle size of the polyvinyl alcohol powder is 1.0-2.0 μm; the antioxidant is magnesium stearate and / or tributyl borate.

9. A method for preparing a magnet having a magnetic isolation layer according to any one of claims 3 to 8, characterized in that: The steps include: S1. According to parts by weight, a mixture of light and heavy rare earths is melted and then crushed to obtain a mixed rare earth alloy powder for later use; S2, according to weight parts, ferrite magnetic powder, NdFeB magnet and high melting point carbide are mixed, and then smelted under the protection of argon gas, and the molten material is rapidly solidified during smelting to obtain a main phase alloy casting sheet for standby use; S3, hydrogen-crushing the main phase alloy flakes to obtain main phase powders, adding the mixed rare earth alloy powders, antioxidants and binders to the main phase powders, mixing them well, and then crushing them into powders of 2.5-3.5 μm by jet milling for later use; S4, placing the powder obtained in step S3 in a magnetic field with a magnetic field strength of 1.5-3.5T under the protection of an inert gas for orientation and shaping, and then subjecting the powder to static pressing at a pressure of 600-800MPa to obtain a magnet blank for standby use; S5, sintering the magnet blank at 1000-1100°C for 5-9h with a heating rate of 8-12°C / min, and then subjecting the magnet blank to primary and secondary tempering to obtain a magnet for standby use; S6, preheating the surface of the magnet obtained in step S5 to 170-200° C., then spraying the magnetic isolation layer particles on the surface of the preheated magnet by plasma spraying to obtain a magnetic isolation coating, and finally obtaining a magnet with a magnetic isolation layer.