Sintered samarium-cobalt magnet and preparation method thereof

Abstract

The invention discloses a sintered samarium-cobalt magnet and a preparation method thereof. The preparation method of the sintered samarium-cobalt magnet comprises the following steps: 1) providing required alloy raw materials according to the chemical composition of the sintered samarium-cobalt magnet, and smelting the alloy raw materials to prepare an alloy ingot; 2) carrying out coarse crushing on the alloy ingot to obtain intermediate crushed powder, and then grinding the intermediate crushed powder into samarium cobalt alloy fine powder with the average particle size D50 of 5.5-7.5 microns; (3) the samarium-cobalt alloy fine powder and the ZrB2 powder are mixed, and mixed powder is prepared; 4) screening the mixed powder to obtain undersize powder; 5) performing magnetic field orientation and isostatic pressing treatment on the undersize powder to obtain a pressed blank; and 6) sintering the pressed blank at 1160-1240 DEG C, then carrying out solid solution at 1140-1180 DEG C, and then carrying out aging treatment at 800-850 DEG C to obtain the sintered samarium-cobalt magnet. The sintered samarium-cobalt magnet prepared by the preparation method disclosed by the invention has relatively good bending strength and intrinsic coercive force at the same time.

Description

Technical Field

[0001] The present invention relates to a sintered samarium cobalt magnet and a preparation method thereof. Background Art

[0002] Samarium cobalt permanent magnet materials are a kind of high-performance rare earth permanent magnet materials developed in the 1960s and 1970s of the 20th century. Because of their unique advantages such as high working temperature, small temperature coefficient, and strong corrosion resistance, they are widely used in military, aerospace, microwave equipment, communication, instruments and meters and other fields. Compared with neodymium iron boron rare earth permanent magnet materials, samarium cobalt permanent magnet materials have a higher Curie temperature and play an important role in specific fields. Although the market share of samarium cobalt permanent magnet materials is low, their irreplaceability is significant. Due to the lack of slip deformation mode and poor ductility of samarium cobalt materials, problems such as edge defects, corner breakage, cracking, and fragmentation are prone to occur during the product processing. On the grinding machine, the edges and corners are easily turned into serrated shapes, so that their scope of use is limited and the rejection rate is high.

[0003] There is a mutual restriction relationship between the magnetic properties and mechanical properties of samarium cobalt permanent magnet materials. For a long time, those skilled in the art have mainly focused on improving the magnetic properties of samarium cobalt permanent magnet materials, and less research has been done on their mechanical properties. The existing research on improving mechanical properties mainly starts from aspects such as surface modification and element doping. In recent years, researchers have carried out a large amount of research work on it. Although the mechanical properties of the magnet can be improved by adding a second phase during powder making, the powder of the magnet will agglomerate after adding the second phase, resulting in a significant reduction in the magnetic properties of the magnet.

[0004] CN107316726A discloses a preparation method of a sintered samarium cobalt magnet. The preparation method includes: (1) preparation of alloy powder, preparing a samarium cobalt alloy raw material according to the following weight percentages: (Sm1-xRx): 25-27%, Fe: 6-25%, Zr: 2-3.5%, Cu: 3-8%, and the balance is Co, 0≤x≤0.9; wherein, R is one or more of Ce, Pr, Nd, Gd, Tb, Dy, Ho, and Er; through melting, casting, and mechanical crushing; and then making alloy powder by oxygen-supplemented airflow milling technology; (2) cleaning, crushing, conventional airflow milling, and fully mixing with a lubricant of the leftover materials and waste materials with compositions similar to those of the alloy powder to make auxiliary powder; (3) mixing, mixing the alloy powder and the auxiliary powder in proportion to obtain samarium cobalt alloy powder; (4) magnetic field forming and isostatic pressing to prepare a green body; (5) sintering and solid solution and aging treatment to prepare a sintered samarium cobalt magnet. Although this preparation method can improve the mechanical properties by cooperating with the oxygen-supplemented airflow milling technology, it will cause the intrinsic coercivity of the prepared sintered samarium cobalt magnet to decrease and the magnetic properties to be poor. And the detection of the mechanical properties of the sintered samarium cobalt magnet is not involved in this patent document either.

[0005] CN112582124A discloses a preparation method of a sintered samarium cobalt magnet. The preparation method includes: 1) preparation of alloy powder a, 2) preparation of auxiliary material b, 3) powder mixing, 4) hydrogen breaking to prepare powder, 5) magnetic powder passivation treatment, 6) magnetic field forming and isostatic pressing, 7) sintering solid solution and aging treatment. Four kinds of alloy powders need to be prepared in the process of preparing the sintered samarium cobalt magnet by this preparation method. Alloy b powder needs to be cleaned, dried and mechanically crushed. Alloy d powder needs to be prepared through pressure holding, hydrogen absorption, heating, pressure holding, hydrogen absorption and dehydrogenation. The process is cumbersome and time-consuming in production, which is not conducive to mass production preparation. Moreover, the magnetic properties of the sintered samarium cobalt magnet prepared by this preparation method are not good.

[0006] CN112582121A discloses a preparation method of a super high performance sintered samarium cobalt magnet. The method includes: 1) preparation of ingot a; 2) preparation of ingot b; 3) powder making; 4) powder mixing and passivation; 5) magnetic field forming and isostatic pressing; 6) sintering solid solution and aging treatment. The ingot is wrapped with iron sheet and then remelted in a high-pressure and high-purity inert atmosphere, which takes a lot of time. At the same time, oxygen is supplemented during powder mixing, which will reduce the magnetic properties of the magnet.

[0007] CN119274907A discloses a samarium cobalt magnet with high mechanical properties and its preparation method. The preparation method includes a powder laying and pressing step, in which samarium cobalt A powder and samarium cobalt B powder are alternately laid, ensuring that the bottom layer and the top layer are samarium cobalt B powder, and the particle sizes of samarium cobalt A powder and samarium cobalt B powder are different; the weight of the samarium cobalt A powder is 5-50 wt%, and the weight of the samarium cobalt B powder is 95-50 wt%. This preparation method alternately arranges samarium cobalt A powder and samarium cobalt B powder with different particle sizes, ensuring that the bottom layer and the top layer are samarium cobalt B powder. The preparation process is too cumbersome, which is not conducive to mass production in production, and the magnetic properties of the prepared samarium cobalt magnet are not good. Summary of the Invention

[0008] In view of this, an object of the present invention is to provide a preparation method of a sintered samarium cobalt magnet, and the sintered samarium cobalt magnet prepared by this preparation method has good bending strength and intrinsic coercivity at the same time. Another object of the present invention is to provide a sintered samarium cobalt magnet prepared by the above preparation method. Still another object of the invention is to provide the use of ZrB2 in improving the mechanical properties of sintered samarium cobalt magnets.

[0009] The present invention adopts the following technical solutions to achieve the above objects.

[0010] On the one hand, the present invention provides a preparation method of a sintered samarium cobalt magnet, including the following steps:

[0011] 1) Provide the required alloy raw materials according to the chemical composition of the sintered samarium-cobalt magnet, melt the alloy raw materials, and obtain an alloy ingot; wherein, the chemical composition of the sintered samarium-cobalt magnet is as follows by mass percentage: Sm 23-30% wt%, Fe 13-22 wt%, Cu is 5-7 wt%, Zr 1-4 wt%, and the balance is Co and unavoidable impurities;

[0012] 2) Coarsely crush the alloy ingot obtained in step 1) to obtain medium-sized powder, and then grind the medium-sized powder into samarium-cobalt alloy fine powder with an average particle size D 50 of 5.5-7.5 μm;

[0013] 3) Mix the samarium-cobalt alloy fine powder obtained in step 2) with ZrB2 powder to obtain a mixed powder; wherein, the mass ratio of the samarium-cobalt alloy fine powder to the ZrB2 powder is 99-99.95:0.05-1;

[0014] 4) Screen the mixed powder obtained in step 3) to obtain the undersize powder; wherein, the mesh number of the sieve for screening is 200-600 meshes;

[0015] 5) Perform magnetic field orientation and isostatic pressing on the undersize powder obtained in step 4) to obtain a green compact;

[0016] 6) Sinter the green compact obtained in step 5) at 1160-1240 °C, then perform solid solution at 1140-1180 °C, and then perform aging treatment at 800-850 °C to obtain a sintered samarium-cobalt magnet.

[0017] According to the preparation method of the present invention, preferably, in step 1), the temperature of the melting is 1300-1600 °C, and the melting time is 5-60 min.

[0018] According to the preparation method of the present invention, preferably, in step 2), the coarse crushing is carried out under the protection of a protective gas; the medium-sized powder is ground into samarium-cobalt alloy fine powder under the protection of a protective gas.

[0019] According to the preparation method of the present invention, preferably, in step 3), the average particle size D 50 of the ZrB2 powder is 0.06-15 μm.

[0020] According to the preparation method of the present invention, preferably, in step 4), the number of screenings is 5-10 times.

[0021] According to the preparation method of the present invention, preferably, in step 5), the magnetic field strength of the magnetic field orientation is 1-5 T.

[0022] According to the preparation method of the present invention, preferably, in step 5), the isostatic pressing is cold isostatic pressing, and the pressure of the cold isostatic pressing is 100-500 MPa.

[0023] According to the preparation method of the present invention, preferably, in step 6), the sintering time is 1-10 h, the solution treatment time is 1-10 h, and the aging treatment time is 10-30 h

[0024] On the other hand, the present invention also provides a sintered samarium cobalt magnet prepared by the above preparation method. Preferably, the sintered samarium cobalt magnet is processed into a cuboid with specifications of h×b×l = 5 mm×6 mm×20-28 mm along two different orientation directions. Among them, h is the height of the cuboid, b is the width of the cuboid, and l is the length of the cuboid. The relationships between the two different orientation directions and the easy magnetization axis c-axis are h / / c and b / / c respectively; the bending strength along the h orientation direction is at least 96 MPa, and the bending strength along the b orientation direction is at least 125 MPa;

[0025] The H of the sintered samarium cobalt magnet cj is at least 30 kOe.

[0026] On the other hand, the present invention also provides a use of ZrB2 in improving the mechanical properties of a sintered samarium cobalt magnet. Preferably, the sintered samarium cobalt magnet with improved mechanical properties by ZrB2 is processed into a cuboid with specifications of h×b×l = 5 mm×6 mm×20-28 mm along two different orientation directions. Among them, h is the height of the cuboid, b is the width of the cuboid, and l is the length of the cuboid. The relationships between the two different orientation directions and the easy magnetization axis c-axis are h / / c and b / / c respectively; the bending strength along the h orientation direction is at least 96 MPa, and the bending strength along the b orientation direction is at least 125 MPa;

[0027] The H of the sintered samarium cobalt magnet with improved mechanical properties by ZrB2 cj is at least 30 kOe.

[0028] The sintered samarium cobalt magnet prepared by the present invention has good bending strength and intrinsic coercivity at the same time. The sintered samarium cobalt magnet prepared by the present invention is processed into a cuboid with specifications of h×b×l = 5 mm×6 mm×20-28 mm along two different orientation directions. Among them, h is the height of the cuboid, b is the width of the cuboid, and l is the length of the cuboid. The relationships between the two different orientation directions and the easy magnetization axis c-axis are h / / c and b / / c respectively; the bending strength along the h orientation direction is at least 96 MPa, and the bending strength along the b orientation direction is at least 125 MPa. The H of the sintered samarium cobalt magnet prepared by the present invention cj is at least 30 kOe. Detailed embodiments

[0029] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0030] The "flexural strength" as described in the present invention refers to the maximum flexural stress when the material is bent until fracture, with the unit of megapascal (MPa).

[0031] The "intrinsic coercivity" as described in the present invention refers to the reverse magnetic field strength applied when the vector sum of the microscopic magnetic dipole moments inside the magnet is reduced to 0, usually denoted as H cj , with the unit of kilo - oersted (kOe) or kilo - ampere per meter (kA / m).

[0032] The "average particle size D 50 " represents the equivalent diameter of the largest particle when the cumulative distribution in the particle size distribution curve is 50%.

[0033] <Preparation method of sintered samarium - cobalt magnet>

[0034] The preparation method of the sintered samarium - cobalt magnet of the present invention includes steps of batching and melting, crushing, powder mixing, powder screening, compacting, and heat treatment. Details are described below.

[0035] Ingredient and Melting Steps

[0036] Provide the required alloy raw materials according to the chemical composition of the sintered samarium - cobalt magnet, and melt the alloy raw materials to obtain an alloy ingot.

[0037] According to an embodiment of the present invention, the chemical composition of the sintered samarium - cobalt magnet is as follows by mass percentage: Sm ۲۳ - ۳۰% wt%, Fe ۱۳ - ۲۲ wt%, Cu is ۵ - ۷ wt%, Zr ۱ - ۴ wt%, and the balance is Co and inevitable impurities.

[0038] Preferably, the chemical composition of the sintered samarium - cobalt magnet is as follows by mass percentage: Sm ۲۴ - ۲۸% wt%, Fe ۱۵ - ۲۱ wt%, Cu is ۴.۵ - ۶ wt%, Zr ۱.۵ - ۳.۵ wt%, and the balance is Co and inevitable impurities.

[0039] More preferably, the chemical composition of the sintered samarium - cobalt magnet is as follows by mass percentage: Sm ۲۵ - ۲۷% wt%, Fe ۱۶ - ۲۰ wt%, Cu is ۴ - ۵.۵ wt%, Zr ۲ - ۳ wt%, and the balance is Co and inevitable impurities.

[0040] According to an embodiment of the present invention, the alloy raw materials can be elemental substances of each element or alloys of each element, as long as the mass percentages of the chemical composition of the sintered samarium - cobalt magnet are satisfied.

[0041] The elemental substances or alloys of each element used in the present invention can use commercially available products or can be prepared by existing preparation methods, and no special limitation is made here. The purity of the elemental substances or alloys of each element in the present invention is at least 99.5 wt%.

[0042] According to an embodiment of the present invention, the melting temperature can be 1300 - 1600 °C, preferably 1350 - 1580 °C, and more preferably 1400 - 1550 °C. The melting time can be 5 - 60 min, preferably 10 - 50 min, and more preferably 20 - 40 min.

[0043] The melting of the present invention can be realized in any melting device well known in the art, and no special limitation is made here. For example, but not limited to, it can be a vacuum induction furnace.

[0044] When melting in the present invention, the alloy raw materials can be put into a vessel, and the alloy raw materials are heated together with the vessel. The vessel can be any heating vessel well known in the art, and no special limitation is made here. For example, it can be a high-temperature resistant metal mold or crucible, preferably a crucible.

[0045] According to an embodiment of the present invention, before melting, it can also include the steps of evacuating and filling with a protective gas.

[0046] In the present invention, before melting, it can be evacuated to 0.001 - 5 Pa, preferably 0.01 - 0.5 Pa, and more preferably 0.02 - 0.2 Pa.

[0047] The protective gas involved in the present invention can be selected from at least one of nitrogen and inert gases. The inert gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe); preferably, the protective gas is selected from at least one of nitrogen, helium, neon, and argon; more preferably, the protective gas is selected from at least one of nitrogen, helium, and argon.

[0048] In the present invention, after forming the alloy ingot, it can also include a cooling step. The cooling can be any cooling method well known in the art, and the cooling method can be realized by using any cooling device well known in the art, and no special limitation is made here. For example, but not limited to, it can be water cooling or air cooling.

[0049] A reasonable element ratio and melting conditions are beneficial to grain refinement, increase the precipitation phase at grain boundaries, and at the same time avoid composition segregation, which affects the density of the magnet and reduces magnet defects. This is more conducive to the sintered samarium cobalt magnet having better bending strength and intrinsic coercivity.

[0050] Crushing Step

[0051] The alloy ingot is coarsely crushed to obtain medium-sized powder, and then the medium-sized powder is ground into an average particle size D 50Samarium cobalt alloy fine powder with an average particle size of 5.5 to 7.5 μm.

[0052] According to one embodiment of the present invention, the average particle size D of the medium-crushed powder 50 can be 15 to 60 μm, preferably 20 to 55 μm, and more preferably 25 to 50 μm.

[0053] The coarse crushing of the present invention can be achieved using any coarse crushing device known in the art, and no special limitation is made herein. For example, a medium crusher can be used for coarse crushing.

[0054] According to one embodiment of the present invention, the average particle size D of the samarium cobalt alloy fine powder 50 can be 5.5 to 7.5 μm, preferably 5.8 to 7.2 μm, and more preferably 6 to 7 μm.

[0055] If the particle size is too small, the magnetic properties of the magnet will be reduced. If the particle size is too large, the dispersion strengthening effect cannot be achieved, which is not conducive to improving the mechanical properties of the magnet. A reasonable particle size range can ensure that the sintered samarium cobalt magnet has good bending strength and intrinsic coercivity at the same time.

[0056] According to one embodiment of the present invention, coarse crushing can be carried out under the protection of a protective gas.

[0057] According to one embodiment of the present invention, the medium-crushed powder can also be ground into samarium cobalt alloy fine powder under the protection of a protective gas.

[0058] The protective gas can be selected from at least one of nitrogen and inert gases. The inert gases include helium, neon, argon, krypton, and xenon. Preferably, the protective gas is selected from at least one of nitrogen, helium, neon, and argon. More preferably, the protective gas is selected from at least one of nitrogen, helium, and argon.

[0059] The present invention can use any ultrafine pulverization equipment known in the art to grind the medium-crushed powder into fine powder, and no special limitation is made herein. For example, a jet mill, a ball mill or a disc mill can be used, preferably a jet mill. When using a jet mill, powders with different particle sizes can be obtained by adjusting the rotation speed of the sorting wheel. When using a jet mill, the oxygen content of the jet mill can be controlled ≤ 300 ppm, preferably 10 to 300 ppm, and more preferably 50 to 200 ppm.

[0060] Powder Mixing Step

[0061] Mix the samarium cobalt alloy fine powder with ZrB2 powder to obtain a mixed powder.

[0062] According to an embodiment of the present invention, the mass ratio of samarium cobalt alloy fine powder to ZrB2 powder can be 99-99.95:0.05-1, preferably 99.2-99.92:0.08-0.8, and more preferably 99.5-99.9:0.1-1.

[0063] In the present invention, an intermetallic compound ZrB2 with a melting point above 2500 °C is added to the micron-sized samarium cobalt alloy powder. It can combine with Fe and Co elements to enhance the strength and toughness of the magnet matrix, absorb part of the stress, reduce stress concentration, and improve the mechanical properties of the sintered samarium cobalt material.

[0064] Limiting the mass ratio of samarium cobalt alloy fine powder to ZrB2 powder within the above range is beneficial for the sintered samarium cobalt magnet to have good bending strength and intrinsic coercivity simultaneously.

[0065] According to an embodiment of the present invention, the average particle size D of the ZrB2 powder 50 can be 0.06-15 μm, preferably 0.08-12 μm, and more preferably 0.1-10 μm.

[0066] A reasonable particle size range can ensure that the sintered samarium cobalt magnet has good bending strength and intrinsic coercivity simultaneously.

[0067] In the present invention, any mixing equipment known in the art can be used to achieve mixing, and no special limitation is made here. For example, a three-dimensional motion mixer can be used.

[0068] According to an embodiment of the present invention, the mixing time can be 1-5 h, preferably 1-4 h, and more preferably 2-4 h. A reasonable mixing time can ensure more uniform mixing of the powders, which is beneficial for the sintered samarium cobalt magnet to have good bending strength and intrinsic coercivity simultaneously.

[0069] Powder Screening Step

[0070] The mixed powder is screened to obtain the undersize powder.

[0071] According to an embodiment of the present invention, the mesh number of the sieve for screening can be 200-600 mesh, preferably 250-550 mesh, and more preferably 300-500 mesh.

[0072] According to an embodiment of the present invention, the number of screening times can be 5-10 times, preferably 5-8 times, and more preferably 6-8 times.

[0073] Reasonable screening conditions are beneficial for the dispersion of the powder, prevent powder agglomeration, and are more beneficial for the sintered samarium cobalt magnet to have good bending strength and intrinsic coercivity simultaneously.

[0074] According to an embodiment of the present invention, the screening can be carried out under the protection of a protective gas.

[0075] The protective gas can be selected from at least one of nitrogen and inert gases, and the inert gases include helium, neon, argon, krypton, and xenon; preferably, the protective gas is selected from at least one of nitrogen, helium, neon, and argon; more preferably, the protective gas is selected from at least one of nitrogen, helium, and argon.

[0076] Billet Making Step

[0077] The powder passing through the sieve is subjected to magnetic field orientation and isostatic pressing to obtain a green compact.

[0078] According to an embodiment of the present invention, the magnetic field strength for magnetic field orientation can be 1 - 5 T, preferably 1 - 3 T, and more preferably 1.5 - 3 T.

[0079] According to an embodiment of the present invention, the magnetic field orientation and the magnetic powder pressing direction are parallel or perpendicular to each other.

[0080] According to an embodiment of the present invention, isostatic pressing is preferably cold isostatic pressing, and the pressure of cold isostatic pressing can be 100 - 500 Mpa, preferably 200 - 450 Mpa, and more preferably 250 - 400 Mpa.

[0081] A reasonable magnetic field strength and pressure are beneficial for the sintered samarium - cobalt magnet to have good bending strength and intrinsic coercivity simultaneously.

[0082] In the present invention, the shape of the green compact can be any shape well - known in the art and is not particularly limited herein. For example, but not limited to, it can be a cuboid. When the green compact is a cuboid, the length of the cuboid can be 35 - 65 cm, preferably 40 - 60 cm, and more preferably 45 - 55 cm. The width of the cuboid can be 30 - 60 cm, preferably 35 - 55 cm, and more preferably 40 - 50 cm. The height of the cuboid can be 40 - 70 cm, preferably 45 - 65 cm, and more preferably 50 - 60 cm.

[0083] Heat Treatment Step

[0084] The green compact is sintered at 1160 - 1240 °C, then solid - solved at 1140 - 1180 °C, and then aged at 800 - 850 °C to obtain a sintered samarium - cobalt magnet.

[0085] According to an embodiment of the present invention, the sintering temperature can be 1160 - 1240 °C, preferably 1170 - 1220 °C, and more preferably 1180 - 1200 °C. The sintering time can be 1 - 10 h, preferably 2 - 8 h, and more preferably 3 - 6 h.

[0086] The sintering of the present invention can be achieved in any sintering device well-known in the art, and no special limitation is made here. For example, but not limited to, it can be a vacuum sintering furnace.

[0087] According to an embodiment of the present invention, before sintering, the sintering device can also be evacuated to a pressure of 0.001 - 1 Pa, preferably 0.005 - 0.1 Pa, and more preferably 0.006 - 0.05 Pa.

[0088] According to an embodiment of the present invention, the solution treatment temperature can be 1140 - 1180 °C, preferably 1150 - 1175 °C, and more preferably 1160 - 1170 °C. The solution treatment time can be 1 - 10 h, preferably 1.5 - 8 h, and more preferably 2 - 6 h.

[0089] The solution treatment of the present invention can be achieved in any solution treatment device well-known in the art, and no special limitation is made here. For example, but not limited to, it can be a solution furnace or a solution aging furnace. In view of the need for aging treatment after solution treatment in the present invention, it is preferred to use a solution aging furnace.

[0090] According to an embodiment of the present invention, the aging treatment temperature can be 800 - 850 °C, preferably 810 - 840 °C, and more preferably 815 - 830 °C. The aging treatment time can be 10 - 30 h, preferably 12 - 28 h, and more preferably 15 - 25 h.

[0091] The aging treatment of the present invention can be achieved in any aging treatment device well-known in the art, and no special limitation is made here. For example, but not limited to, it can be an aging furnace or a solution aging furnace. In view of the need for solution treatment before aging in the present invention, it is preferred to use a solution aging furnace.

[0092] Reasonable heat treatment conditions are beneficial for the sintered samarium cobalt magnet to simultaneously have good bending strength and intrinsic coercivity.

[0093] <Sintered Samarium Cobalt Magnet>

[0094] The present invention also provides a sintered samarium cobalt magnet prepared by the above preparation method. The sintered samarium cobalt magnet of the present invention is a 2:17 type samarium cobalt permanent magnet.

[0095] According to an embodiment of the present invention, the sintered samarium cobalt magnet is processed into a cuboid with specifications of h×b×l = 5 mm×6 mm×20 - 28 mm, where h is the height of the cuboid, b is the width of the cuboid, and l is the length of the cuboid. The relationships between the two different orientation directions and the easy magnetization axis c-axis are h / / c (h is parallel to c) and b / / c (b is parallel to c) respectively; the bending strength along the h orientation direction is at least 96 MPa, and the bending strength along the b orientation direction is at least 125 MPa.

[0096] The bending strength in the h - orientation direction refers to the bending strength measured by applying a force parallel to the plane where the h - side is located. The bending strength in the b - orientation direction refers to the bending strength measured by applying a force perpendicular to the plane where the b - side is located.

[0097] According to a specific embodiment of the present invention, the sintered samarium - cobalt magnet can be processed into a cuboid with dimensions of h×b×l = 5 mm×6 mm×20 - 28 mm, preferably a cuboid with dimensions of h×b×l = 5 mm×6 mm×22 - 26 mm, and more preferably a cuboid with dimensions of h×b×l = 5 mm×6 mm×23 - 25 mm.

[0098] According to a specific embodiment of the present invention, the bending strength in the h - orientation direction can be at least 96 MPa, preferably at least 96.5 MPa, and more preferably at least 97 MPa. The bending strength in the b - orientation direction can be at least 125 MPa, preferably at least 125.5 MPa, and more preferably at least 126 MPa.

[0099] According to an embodiment of the present invention, the H of the sintered samarium - cobalt magnet cj can be at least 30 kOe, preferably at least 30.1 kOe, and more preferably at least 30.11 kOe.

[0100] <Use>

[0101] The present invention provides a use of ZrB2 in improving the mechanical properties of sintered samarium - cobalt magnets.

[0102] According to an embodiment of the present invention, the sintered samarium - cobalt magnet with improved mechanical properties by ZrB2 is processed into a cuboid with dimensions of h×b×l = 5 mm×6 mm×20 - 28 mm, where h is the height of the cuboid, b is the width of the cuboid, and l is the length of the cuboid. The relationships between the two different orientation directions and the easy - magnetization axis c - axis are h / / c (h is parallel to c) and b / / c (b is parallel to c) respectively; the bending strength in the h - orientation direction is at least 96 MPa, and the bending strength in the b - orientation direction is at least 125 MPa.

[0103] The bending strength in the h - orientation direction refers to the bending strength measured by applying a force parallel to the plane where the h - side is located. The bending strength in the b - orientation direction refers to the bending strength measured by applying a force perpendicular to the plane where the b - side is located.

[0104] According to a specific embodiment of the present invention, the sintered samarium - cobalt magnet can be processed into a cuboid with dimensions of h×b×l = 5 mm×6 mm×20 - 28 mm, preferably a cuboid with dimensions of h×b×l = 5 mm×6 mm×22 - 26 mm, and more preferably a cuboid with dimensions of h×b×l = 5 mm×6 mm×23 - 25 mm.

[0105] According to a specific embodiment of the present invention, the flexural strength along the h orientation direction can be at least 96 MPa, preferably at least 96.5 MPa, and more preferably at least 97 MPa. The flexural strength along the b orientation direction can be at least 125 MPa, preferably at least 125.5 MPa, and more preferably at least 126 MPa.

[0106] According to an embodiment of the present invention, the H of the sintered samarium cobalt magnet after improving the mechanical properties by ZrB2 cj can be at least 30 kOe, preferably at least 30.1 kOe, and more preferably at least 30.11 kOe.

[0107] <Test method>

[0108] Measurement of intrinsic coercivity: Test using a Hirst ultra-high coercivity permanent magnet measuring instrument.

[0109] Measurement of flexural strength: Refer to GB / T 31967.2-2015 and test using an Instron universal material testing machine.

[0110] <Raw material description>

[0111] The raw materials in the following examples are all commercially available products unless otherwise specified.

[0112] Among them, the ultrasonic sieving machine is model SF-150, the frequency is 24 - 36 kHz, and the pulser is continuous for 0.1 s - 10 s.

[0113] Example 1

[0114] Preparation of sintered samarium cobalt magnet:

[0115] 1) Batching and melting:

[0116] The chemical composition of the sintered samarium cobalt magnet in this embodiment is as follows by mass percentage: Sm 25.5 wt%, Fe 16 wt%, Cu 5.5 wt%, Zr 3 wt%, and the balance is Co and unavoidable impurities;

[0117] Complete batching according to the alloy raw materials of the sintered samarium cobalt magnet.

[0118] Place the prepared alloy components in a crucible, place the crucible in a vacuum induction furnace, then evacuate to a pressure of 0.04 Pa and fill with argon, and then melt at 1510 °C for 25 min to melt the alloy raw materials and obtain an alloy ingot.

[0119] 2) Crushing: Coarsely crush the alloy ingot through a medium crusher to obtain an average particle size D 50Medium-sized crushed powder with a size of 25 μm; then, using a jet mill, the medium-sized crushed powder was ground into samarium cobalt alloy fine powder with an average particle size D 50 of 6.2 μm under the condition that the oxygen content was 100 ppm.

[0120] 3) Powder mixing: The samarium cobalt alloy fine powder and ZrB2 powder with an average particle size D 50 of 1 μm were placed in a three-dimensional motion mixer according to a mass ratio of 99.9:0.1 and mixed for 2 h to obtain a mixed powder.

[0121] 4) Sieving the powder: The mixed powder was placed in an ultrasonic sieving machine and sieved 7 times with a 400-mesh sieve under the conditions of a frequency of 36 kHz and nitrogen protection to obtain the undersize powder.

[0122] 5) Blanking: The undersize powder was oriented and formed under a magnetic field strength of 1.7 T, and then isostatic pressing was carried out at 280 Mpa to obtain a rectangular blank with a length of 52 mm, a width of 49 mm, and a height of 55 mm, where the magnetic orientation was in the height direction.

[0123] 6) Heat treatment: The blank was placed in a vacuum sintering furnace, evacuated to a pressure of 0.01 Pa, and sintered at 1185 °C for 4 h; the sintered blank was placed in a solution aging furnace, solutionized at 1170 °C for 2 h, and aged at 820 °C for 20 h to obtain a sintered samarium cobalt magnet.

[0124] Example 2

[0125] Except for the following parameters and settings, the rest were the same as in Example 1:

[0126] In this example, the samarium cobalt alloy fine powder and ZrB2 powder with an average particle size D 50 of 1 μm were placed in a three-dimensional motion mixer according to a mass ratio of 99.8:0.2 and mixed for 2 h to obtain a mixed powder.

[0127] Example 3

[0128] Except for the following parameters and settings, the rest were the same as in Example 1:

[0129] In this example, the samarium cobalt alloy fine powder and ZrB2 powder with an average particle size D 50 of 0.1 μm were placed in a three-dimensional motion mixer according to a mass ratio of 99.7:0.3 and mixed for 2 h to obtain a mixed powder.

[0130] Example 4

[0131] Except for the following parameters and settings, the rest were the same as in Example 1:

[0132] In this embodiment, samarium-cobalt alloy fine powder and ZrB2 powder with an average particle size D 50 of 0.1 μm were placed in a three-dimensional motion mixer according to a mass ratio of 99.8:0.2 and mixed for 2 h to obtain a mixed powder.

[0133] Example 5

[0134] Except for the following parameters and settings, the rest are the same as in Example 1:

[0135] In this embodiment, samarium-cobalt alloy fine powder and ZrB2 powder with an average particle size D 50 of 10 μm were placed in a three-dimensional motion mixer according to a mass ratio of 99.8:0.2 and mixed for 2 h to obtain a mixed powder.

[0136] Comparative Example 1

[0137] Preparation of sintered samarium-cobalt magnet:

[0138] 1) Batching and melting:

[0139] The chemical composition of the sintered samarium-cobalt magnet in this embodiment is as follows by mass percentage: Sm 25.5 wt%, Fe 16 wt%, Cu 5.5 wt%, Zr 3 wt%, and the balance is Co and unavoidable impurities;

[0140] According to the alloy raw materials of the sintered samarium-cobalt magnet, batching was completed.

[0141] The prepared alloy components were placed in a crucible, and the crucible was placed in a vacuum induction furnace. Then, the vacuum was pumped to a pressure of 0.04 Pa and argon was filled. Then, it was melted at 1510 °C for 25 min to melt the alloy raw materials and obtain an alloy ingot.

[0142] 2) Crushing: The alloy ingot was coarsely crushed by a medium crusher to obtain medium-crushed powder with an average particle size D 50 of 25 μm; then, using a jet mill, the medium-crushed powder was ground into samarium-cobalt alloy fine powder with an average particle size D 50 of 6.2 μm under the condition of an oxygen content of 100 ppm.

[0143] 3) Blanking: The samarium-cobalt alloy fine powder was oriented and formed under a magnetic field strength of 1.7 T, and then isostatic pressing treatment was carried out at 280 Mpa to obtain a rectangular blank with a length of 52 mm, a width of 49 mm, and a height of 55 mm, where the magnetic orientation is in the height direction.

[0144] 4) Heat treatment: Place the green compact in a vacuum sintering furnace, evacuate to a pressure of 0.01 Pa, and sinter at 1185 °C for 4 h; place the sintered green compact in a solution heat treatment and aging furnace, perform solution heat treatment at 1170 °C for 2 h, and perform aging treatment at 820 °C for 20 h to obtain a sintered samarium cobalt magnet.

[0145] Comparative Example 2

[0146] Preparation of sintered samarium cobalt magnet:

[0147] 1) Batching and melting:

[0148] The chemical composition of the sintered samarium cobalt magnet in this embodiment is as follows by mass percentage: Sm 25.5 wt%, Fe 16 wt%, Cu 5.5 wt%, Zr 3 wt%, and the balance is Co and unavoidable impurities;

[0149] Complete batching according to the alloy raw materials of the sintered samarium cobalt magnet.

[0150] Place the prepared alloy components in a crucible, place the crucible in a vacuum induction furnace, then evacuate to a pressure of 0.04 Pa and fill with argon gas, and then melt at 1510 °C for 25 min to melt the alloy raw materials and obtain an alloy ingot.

[0151] 2) Crushing: Coarsely crush the alloy ingot through an intermediate crusher to obtain intermediate crushed powder with an average particle size D 50 of 25 μm; then, use a jet mill to grind the intermediate crushed powder into samarium cobalt alloy fine powder with an average particle size D 50 of 6.2 μm under the condition of an oxygen content of 100 ppm.

[0152] 3) Powder mixing: Place the samarium cobalt alloy fine powder and ZrB2 powder with an average particle size D 50 of 1 μm in a three-dimensional motion mixer according to a mass ratio of 99.9:0.1 and mix for 2 h to obtain a mixed powder.

[0153] 4) Green compact preparation: Orient and form the mixed powder under a magnetic field strength of 1.7 T, and then perform isostatic pressing at 280 Mpa to obtain a cuboid green compact with a length of 52 mm, a width of 49 mm, and a height of 55 mm, where the magnetic orientation is in the height direction.

[0154] [[ID=3,6]]5) Heat treatment: Place the green compact in a vacuum sintering furnace, evacuate to a pressure of 0.01 Pa, and sinter at 1185 °C for 4 h; place the sintered green compact in a solution heat treatment and aging furnace, perform solution heat treatment at 1170 °C for 2 h, and perform aging treatment at 820 °C for 20 h to obtain a sintered samarium cobalt magnet.

[0155] Comparative Example 3

[0156] Except for the following parameters and settings, the rest are the same as in Comparative Example 2:

[0157] In this embodiment, samarium cobalt alloy fine powder and ZrB2 powder with an average particle size D 50 of 1 μm were placed in a three-dimensional motion mixer according to a mass ratio of 99.8:0.2 and mixed for 2 h to obtain a mixed powder.

[0158] Experimental Example 1

[0159] The following tests were performed on the sintered samarium cobalt magnets prepared in Examples 1 to 5 and Comparative Examples 1 to 3:

[0160] 1. Measure the intrinsic coercivity (H cj ) of the sintered samarium cobalt magnet.

[0161] 2. The sintered samarium cobalt magnet was processed into a cuboid sample with specifications of h×b×l = 5 mm×6 mm×24 mm along two different orientation directions. Among them, h is the height of the cuboid, b is the width of the cuboid, and l is the length of the cuboid. The relationships between the two different orientation directions and the easy magnetization axis c-axis are h / / c and b / / c, respectively. Measure the flexural strength of the sample along the h orientation direction and the b orientation direction, respectively.

[0162] The test results are shown in Table 1.

[0163] Table 1

[0164]

[0165]

[0166] As can be seen from Table 1, the sintered samarium cobalt magnet of the present invention has good intrinsic coercivity while having a high flexural strength. In Comparative Example 1, ZrB2 was not added, and the flexural strength of the sintered samarium cobalt magnet was poor. In Comparative Examples 2 and 3, sieving was not performed, and the flexural strength of the sintered samarium cobalt magnet was poor.

[0167] The present invention is not limited to the above embodiments. Without departing from the essence of the present invention, any deformation, improvement, or replacement that those skilled in the art can think of falls within the scope of the present invention.

Claims

1. A method for preparing a sintered samarium-cobalt magnet, comprising the following steps: 1) providing alloy raw materials according to the chemical composition of a sintered samarium-cobalt magnet, and smelting the alloy raw materials to produce an alloy ingot; wherein the chemical composition of the sintered samarium-cobalt magnet is as follows in percentage by mass: Sm 23-30% by weight, Fe 13-22% by weight, Cu 5-7% by weight, Zr 1-4% by weight, and the balance being Co and unavoidable impurities; 2) The alloy ingot obtained in step 1) is coarsely crushed to obtain medium powder, and then the medium powder is ground into an average particle size D 50 The fine powder of samarium cobalt alloy is 5.5 to 7.5 μm; 3) mixing the samarium-cobalt alloy fine powder obtained in step 2) with ZrB2 powder to obtain a mixed powder; wherein the mass ratio of the samarium-cobalt alloy fine powder to the ZrB2 powder is 99-99.95:0.05-1; 4) Sieving the mixed powder obtained in step 3) to obtain undersize powder; wherein the mesh size of the sieve is 200 to 600 mesh; 5) subjecting the undersize powder obtained in step 4) to magnetic field orientation and isostatic pressing to produce a compact; 6) The compact obtained in step 5) is sintered at 1160-1240° C., followed by solution treatment at 1140-1180° C., and then aging treatment at 800-850° C. to obtain a sintered samarium cobalt magnet.

2. The preparation method according to claim 1, characterized in that In step 1), the smelting temperature is 1300-1600° C., and the smelting time is 5-60 minutes.

3. The preparation method according to claim 1, characterized in that In step 2), coarse crushing is performed under the protection of protective gas; and medium crushed powder is ground into samarium-cobalt alloy fine powder under the protection of protective gas.

4. The preparation method according to claim 1, characterized in that In step 3), the average particle size D of the ZrB2 powder is 50 0.06~15μm.

5. The preparation method according to claim 1, characterized in that In step 4), the screening is performed 5 to 10 times.

6. The preparation method according to claim 1, characterized in that In step 5), the magnetic field intensity of the magnetic field orientation is 1 to 5T.

7. The preparation method according to claim 1, characterized in that In step 5), the isostatic pressing is cold isostatic pressing, and the pressure of the cold isostatic pressing is 100 to 500 MPa.

8. The preparation method according to claim 1, characterized in that In step 6), the sintering time is 1 to 10 hours, the solution treatment time is 1 to 10 hours, and the aging treatment time is 10 to 30 hours.

9. A sintered samarium-cobalt magnet prepared according to the preparation method according to any one of claims 1 to 8, characterized in that: The sintered samarium cobalt magnet is processed into a rectangular parallelepiped with a specification of h×b×l=5mm×6mm×20-28mm along two different orientation directions, wherein h is the height of the rectangular parallelepiped, b is the width of the rectangular parallelepiped, and l is the length of the rectangular parallelepiped. The relationships between the two different orientation directions and the easy magnetization axis c are h / / c and b / / c, respectively. The bending strength along the h orientation direction is at least 96MPa, and the bending strength along the b orientation direction is at least 125MPa. The H of the sintered SmCo magnet cj At least 30kOe.

10. A use of ZrB2 in improving the mechanical properties of sintered samarium cobalt magnets, characterized in that: The sintered samarium cobalt magnet, after mechanical properties have been enhanced by ZrB2, is processed into a rectangular parallelepiped with specifications of h×b×l=5mm×6mm×20-28mm along two different orientation directions, wherein h is the height of the rectangular parallelepiped, b is the width of the rectangular parallelepiped, and l is the length of the rectangular parallelepiped. The relationships between the two different orientation directions and the easy magnetization axis c are h / / c and b / / c, respectively. The bending strength along the h orientation direction is at least 96MPa, and the bending strength along the b orientation direction is at least 125MPa. H of sintered SmCo magnets with mechanical properties improved by ZrB2 cj At least 30kOe.

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