Preparation method of 2: 17 type samarium cobalt permanent magnet

Abstract

The invention relates to a preparation method of a 2: 17 type samarium-cobalt permanent magnet, belongs to the technical field of metallurgical impurity removal, and solves the problems that rare earth samarium is greatly oxidized in the smelting and heat treatment process when the samarium-cobalt permanent magnet is prepared in the prior art, the oxidation loss of the rare earth samarium is large, and the performance of the magnet is not high due to oxide obstruction. A preparation method of a 2: 17 type samarium-cobalt permanent magnet comprises the steps that a vacuum induction furnace is adopted for smelting a metal raw material composed of multiple elementary substances, after the metal raw material is molten by 70%-100%, a strong reducing agent is added, and liquid alloy is obtained along with smelting of the metal raw material; the liquid alloy is subjected to pouring, powdering and profiling, and a permanent magnet blank is obtained; and performing micro-high-pressure sintering on the permanent magnet blank, and performing heat treatment to obtain the samarium-cobalt permanent magnet. And the preparation of the high-magnetic-performance samarium-cobalt permanent magnet is realized.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical impurity removal, and in particular to a method for preparing a 2:17 type samarium cobalt permanent magnet. Background Art

[0002] Samarium cobalt permanent magnet material is an important functional material, widely used in speakers, motors, magnetic machinery, generators, devices for guiding charged particles, actuators, aerospace instruments, etc., and therefore has become a research hotspot in today's science and technology, and plays an irreplaceable role in daily life.

[0003] Sm-Co permanent magnets are divided into 1:5 samarium-cobalt alloy and 2:17 samarium-cobalt alloy, which are mainly prepared by powder metallurgy. However, due to the presence of rare earth materials in the raw materials and production process of these magnets, they are inevitably oxidized to form impurity phases. 17 In addition to the 2:17R, 1:5H and 1:3R phases, there are also some common inclusions in the magnet, such as zirconium-rich Zr6 (Co, Fe )23 and rare earth oxide Sm2O3 particles. The Sm2O3 particles are derived from the inevitable oxidation of Sm by oxygen during the manufacturing process. For example, in a Sm(Co bal Fe 0.1 Cu 0.1 Zr 0.033 ) 6.93 In the magnet, the volume fraction of Sm2O3 particles is 2.6%. On the one hand, the formation of Sm2O3 consumes Sm, causing the chemical composition of the alloy matrix to deviate from the nominal bulk composition; on the other hand, Sm2O3 particles hinder the formation of 1:3R phase and the chemical redistribution of the magnet, ultimately deteriorating the magnetic properties. Sm2O3 is usually undesirable for Sm-Co magnets. Therefore, in Sm-Co magnets, the formation of non-magnetic phases and the formation of inclusions and oxidation should be minimized to enable the magnet to obtain greater magnetic properties and coercive force.

[0004] Regarding the research in the field of rare earth impurity removal, the existing technology mainly focuses on the purification of single elements. For example, the purification of Sm mainly utilizes La or Ce to carry out substitution reduction of Sm2O3, and finally obtains the single element Sm with higher purity through high temperature and high pressure distillation. However, during the smelting process of the magnet, oxidation will inevitably occur due to the presence of the rare earth Sm, which will reduce the magnet performance during the final formation process of the samarium cobalt magnet. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a method for preparing a 2:17 type samarium cobalt permanent magnet, so as to solve at least one of the problems in the prior art of preparing samarium cobalt permanent magnets, such as large amounts of oxidation of rare earth samarium during smelting and heat treatment, large oxidation losses of rare earth samarium, and low performance of samarium cobalt magnets.

[0006] The embodiment of the present invention provides a method for preparing a 2:17 type samarium cobalt permanent magnet, which comprises the following steps: using a vacuum induction furnace to smelt metal raw materials composed of multiple single substances; adding a strong reducing agent when the metal raw materials are melted by 70% to 100%, and smelting the metal raw materials to obtain a liquid alloy; the liquid alloy is poured, powdered, and pressed to obtain a permanent magnet blank; the permanent magnet blank is sintered under slightly high pressure and then heat treated to obtain a samarium cobalt permanent magnet.

[0007] Preferably, the strong reducing agent is any one of K, Ca, Na, Mg, Sr, Ba, La, Ce, and Al, or a mixture of multiple thereof.

[0008] Specifically, the weight ratio of the strong reducing agent added to the samarium cobalt magnet ingredients is 0.0001:1 to 0.01:1.

[0009] Illustratively, the order of placing the metal raw materials in vacuum induction melting is cobalt, zirconium, iron, samarium, copper or zirconium, cobalt, iron, copper, samarium from bottom to top, and the metal raw materials are placed loosely on the top and tightly on the bottom.

[0010] Furthermore, the smelting process is as follows: continuously evacuate the material, and after the vacuum degree reaches 0.3-3.0Pa, bake the material with a baking power of 1-15kW for 1-10min, and maintain vacuum during baking; after baking, stop evacuating the material, introduce argon to 60kPa, increase the power to 20-30kW, and smelt for 10-30min; finally, increase the power to 30-40kW again for rapid mixing and stirring, and the stirring time is 0-10min.

[0011] Preferably, the pouring process is: adjusting the power of the vacuum induction melting furnace to 0, allowing the smelted liquid alloy to stand in the melting furnace for a certain period of time, and then pouring it into a water-cooled mold after removing the solid floating matter by slagging, and obtaining an alloy ingot after cooling.

[0012] Specifically, the powder making process is as follows: the whole powder making process is carried out in an oxygen-free environment, the ingot is placed in a crusher for coarse crushing, and then placed in a jet mill for fine crushing to obtain fine powder, wherein the average particle size of the fine powder is 3 to 5 μm;

[0013] And / or, the pressing process is: compacting the prepared powder in a magnetic field forming press under a magnetic field of 2.0 T, and then performing cold isostatic compaction under a pressure of 200 MPa.

[0014] Furthermore, the sintering process includes: placing the pressed sample into a vacuum high-pressure sintering furnace for sintering, the sintering temperature is 1200° C. to 1230° C., the sintering pressure is 0 to 5 MPa, and the sintering time is 0.5 h to 2 h.

[0015] It should be noted that the heat treatment process includes solution treatment-quenching-aging.

[0016] Preferably, the solution temperature is 1150-1200°C, the time is 2h-10h, and quenching treatment is performed; the aging adopts a staged cooling method, aging at 800-850°C for 20min-10h, cooling at a rate of 0.1-10°C / min, cooling to 300°C-400°C, keeping warm for 1h-20h, and cooling to room temperature with the furnace to obtain a samarium cobalt permanent magnet.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0018] 1. The present invention adjusts the timing of adding the strong reducing agent, that is, during smelting, all the metal raw materials are added to the smelting furnace at the same time for smelting, and the reducing agent is added to carry out accompanying smelting after the metal raw materials are melted by 70% to 100%, so as to remove the floating oxide particles; the oxygen content in the liquid alloy is reduced to below 50ppm, and the oxidation of Sm during the smelting process is reduced. Compared with the air absorption method, the later deoxygenation method, etc., the deoxygenation amount is increased by more than 10%, the reaction time is shortened, and it is ensured that the samarium element in the permanent magnet can still reach the nominal value without adding excessive samarium raw materials, and the content of the strong reducing agent in the samarium-cobalt magnet is less than 200ppm;

[0019] Compared with adding the reducing agent before smelting, the excessive incorporation of Ca into the alloy magnet is reduced; compared with adding metallic samarium and the reducing agent at the same time after smelting for a certain period of time, the excessive volatilization of samarium is effectively avoided.

[0020] 2. The present invention optimizes the sintering process parameters and adopts a micro-high pressure sintering method to improve the density of the alloy, making the sintered magnet more compact and effectively avoiding shrinkage and the formation of tiny holes that affect the overall performance.

[0021] 3. The present invention optimizes the heat treatment process and parameters, and adopts a heat treatment process of solid solution-quenching-stage aging. During the heat treatment process, the excess reducing agent reacts with oxygen first, which helps to reduce the oxidation of samarium, and the oxide formed by the reducing agent helps the magnet alloy to form finer and evenly distributed grains, which is beneficial to improving the magnetic properties of the magnet;

[0022] The aging treatment method of staged cooling is adopted to form a uniform 1:7 phase during the solid solution period, which is transformed into 1:5 phase and 2:17 phase through staged aging, accompanied by the precipitation of 1:3 phase, and the oxide formed by the reducing agent makes the magnet alloy form finer and evenly distributed grains. It can improve the coercivity of the alloy and improve the magnetic properties. The second stage aging treatment adopts the method of furnace cooling to improve the magnetic properties of the magnet by reducing the residual stress inside the material and improving the magnetic domain structure.

[0023] 4. The method of adding a strong reducing agent to remove oxygen during the smelting process of the present invention to prepare a 2:17 type samarium cobalt permanent magnet, the magnetic properties of the prepared samarium cobalt permanent magnet meet the requirements of remanence ≥11kGs, magnetic energy product ≥29MGOe, intrinsic coercive force ≥25kOe, and the mechanical properties are enhanced compared with those without a strong reducing agent, and the flexural strength is ≥180MPa.

[0024] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0026] Figure 1 Flow chart of deoxygenation for preparing 2:17 type samarium cobalt permanent magnets according to the present invention;

[0027] Figure 2 is the Gibbs free energy of the reaction between samarium oxide and calcium according to the present invention that changes with temperature;

[0028] Figure 3 is the Gibbs free energy of the reaction between the metal oxides of the present invention and calcium as a function of temperature. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0030] A specific embodiment of the present invention discloses a method for preparing a 2:17 type samarium cobalt permanent magnet, which comprises the following steps: using a vacuum induction furnace to smelt metal raw materials composed of multiple single substances, adding a strong reducing agent when the metal raw materials are melted by 70% to 100%, and smelting the metal raw materials to obtain a liquid alloy; the liquid alloy is poured, powdered, and pressed to obtain a permanent magnet blank; the permanent magnet blank is sintered at a slightly high pressure and then heat treated to obtain a samarium cobalt permanent magnet.

[0031] Preferably, the strong reducing agent is any one of K, Ca, Na, Mg, Sr, Ba, La, Ce, and Al, or a mixture of multiple thereof.

[0032] like Figure 2 , Figure 3 As shown, the driving force of the reaction between the strong reducing agent Ca and samarium oxide is much higher than that with other metal oxides, which effectively ensures the samarium yield.

[0033] Specifically, the weight ratio of the strong reducing agent added to the samarium cobalt magnet ingredients is 0.0001:1 to 0.01:1.

[0034] Before smelting the raw materials, the oxygen content is initially tested by a nitrogen oxygen analyzer. The O content in the raw materials ranges from 40 to 200 ppm. 1 ppm of oxygen is consumed, and 2.5 ppm of the above-mentioned reducing agent content is required. The amount of reducing agent added is comprehensively determined based on the recovery rate of different reducing agent metals during the smelting process.

[0035] During smelting, all metal raw materials are added to the smelting furnace for smelting at the same time. After the metal raw materials are melted by 70% to 100%, the reducing agent is added for accompanying smelting to remove floating oxide particles; the oxygen content in the liquid alloy is reduced to below 50ppm, the oxidation of Sm during the smelting process is reduced, and the content of the strong reducing agent in the samarium cobalt magnet is less than 200ppm.

[0036] Compared with adding reducing agent before smelting, it reduces the excessive incorporation of Ca into the alloy magnet, thus improving the magnetic properties and toughness of the magnet; the excessive presence of calcium will lead to the formation of non-magnetic phase, reduce the maximum magnetic energy product of the magnet, cause the inhomogeneity of the chemical composition in the magnet, and thus reduce the remanence (Br) and intrinsic coercive force (H) of the magnet. cj ), excessive mixing of calcium will further increase the brittleness of the magnet, reduce its bending strength and impact toughness, and bring difficulties to mechanical processing and application.

[0037] Compared with adding metallic samarium and reducing agent simultaneously after smelting for a certain period of time, the excessive volatilization of samarium is effectively avoided.

[0038] The metal raw materials include samarium, cobalt, copper, iron and zirconium, wherein the atomic ratio of samarium to cobalt, iron, copper and zirconium is between 1:7.5 and 1:8, which meets the nominal requirements of samarium-cobalt alloy.

[0039] Preferably, the order of placing the metal raw materials in vacuum induction melting is cobalt, zirconium, iron, samarium, copper or zirconium, cobalt, iron, copper, samarium from bottom to top, and the metal raw materials are placed in a loose upper and tight lower manner, so that the upper material melts quickly and does not physically stick to the crucible during the melting process.

[0040] Furthermore, the smelting process is as follows: continuously evacuate the material, and after the vacuum degree reaches 0.3-3.0Pa, bake the material with a baking power of 1-15kW for 1-10min, maintain vacuum during baking, stop evacuating the material after baking, introduce argon to 60kPa, increase the power to 20-30kW, and smelt for 10-30min; finally, increase the power to 30-40kW again for rapid mixing and stirring, and the stirring time is 0-10min.

[0041] In the initial stage of the smelting process, low-power high vacuum is used for degassing. The higher the vacuum degree, the less residual gas content and oxygen content in the alloy liquid. Then medium power is used for smelting. Too high power will lead to serious volatilization of Sm, and high power will cause overburning of the alloy. Increasing the power during the stirring process, on the one hand, speeds up the flow of the alloy liquid, helps to remove the gas and impurities generated during the smelting process, thereby improving the purity and quality of the alloy. On the other hand, it makes the components in the alloy liquid mix more evenly, promotes the refinement of the grains in the alloy liquid, and is beneficial to improving the magnetic properties of the samarium cobalt permanent magnet material.

[0042] Furthermore, the method for preparing 2:17 type samarium cobalt permanent magnets by deoxidation, after the metal raw material is smelted, also includes the following steps: pouring, powder making, pressing, sintering and heat treatment.

[0043] Specifically, the pouring process is: adjusting the power of the vacuum induction melting furnace to 0, allowing the smelted liquid alloy to stand in the melting furnace for a certain period of time, and then pouring it into a water-cooled mold after removing the solid floating matter by slagging, and obtaining the alloy ingot after cooling.

[0044] The water-cooled mold casting includes a water-cooled copper mold. The water-cooled mold makes the internal structure of the liquid alloy uniform during the cooling process, which is convenient for subsequent processing.

[0045] Exemplarily, the powder making process is as follows: the whole powder making process is carried out in an oxygen-free environment, the ingot is placed in a crusher for coarse crushing, and then placed in a jet mill for fine crushing to obtain fine powder. The average particle size of the fine powder is 3 to 5 um, which ensures the consistency and uniformity of the structure of each particle on the one hand, and is beneficial to maintaining tightness during the subsequent alloy sintering process on the other hand.

[0046] The oxygen-free environment includes being carried out in a vacuum glove box.

[0047] Preferably, the pressing process is: compacting the prepared powder in a magnetic field forming press under a magnetic field of 2.0 T, and then performing cold isostatic compaction under a pressure of 200 MPa.

[0048] Furthermore, the sintering process includes: placing the pressed product into a vacuum high-pressure sintering furnace for sintering, the sintering temperature is 1200℃~1230℃, the sintering pressure is 0~5Mpa, and the sintering time is 0.5h~2h. Preferably, the sintering temperature is 1200℃, 1205℃, 1210℃, 1215℃, 1220℃, 1225℃, 1230℃, the sintering pressure is 0.5Mpa, 1Mpa, 2Mpa, 3Mpa, 4Mpa, 5Mpa, and the sintering time is 0.5h, 1h, 1.3h, 1.6h, 2h.

[0049] In the temperature range of 1200℃~1230℃, part of the product reaches the melting point and turns into liquid, but the whole is not completely melted. The collapse and shrinkage in this state are used to complete the sintering. The micro-high pressure sintering method is used to make the density of the alloy higher and the sintered magnet more compact, avoiding the shrinkage and formation of tiny holes that affect the overall performance.

[0050] Furthermore, the heat treatment includes solution treatment-quenching-aging.

[0051] Specifically, the solution temperature is 1150-1200°C, the time is 2h-10h, and then quenching (rapid water cooling) is performed to room temperature. Specifically, the solution temperature is 1150°C, 1160°C, 1170°C, 1180°C, 1190°C, 1200°C, and the solution time is 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h.

[0052] Quenching after solid solution helps to form an unstable uniform phase, which is beneficial to the subsequent aging treatment to form a uniform and stable magnet phase and improve the magnetic properties of the magnet.

[0053] Exemplarily, the aging is carried out in a staged cooling manner. In the first stage, the aging is carried out at 800-850°C for 20min-10h, and the temperature is lowered at a rate of 0.1-10°C / min. In the second stage, the temperature is lowered to 300-400°C, kept at this temperature for 1h-20h, and then cooled to room temperature with the furnace to obtain a samarium cobalt permanent magnet.

[0054] Specifically, the aging temperature of the first stage is 800°C, 8110°C, 820°C, 830°C, 840°C, and 850°C; the aging holding time is 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, and 10h; and the cooling rate is 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, and 9°C / min.

[0055] Preferably, the aging temperature in the second stage is 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, and the aging holding time is 1h, 5h, 8h, 10h, 12h, 15h, 18h, 20h;

[0056] It should be noted that the second stage aging treatment adopts the method of furnace cooling to improve the magnetic properties of the magnet by reducing the residual stress inside the material and improving the magnetic domain structure.

[0057] By adopting the aging treatment method of staged cooling, the uniform 1:7 phase formed in the solid solution period is transformed into 1:5 phase and 2:17 phase through staged aging, accompanied by the precipitation of 1:3 phase, which can increase the coercivity of the alloy and improve the magnetic properties.

[0058] In summary, the present invention reduces the oxygen content in the liquid alloy to below 50 ppm by adding a strong reducing agent to deoxidize during the smelting process and optimizing the order of adding the metal raw material and the reducing agent, thereby reducing the oxidation of Sm during the smelting process, and the content of the strong reducing agent in the samarium cobalt magnet is less than 200 ppm; by optimizing the sintering and heat treatment process parameters, the magnetic properties of the prepared samarium cobalt permanent magnet meet the requirements of remanence ≥11 kGs, magnetic energy product ≥29 MGOe, intrinsic coercive force ≥25 kOe, and bending strength ≥180 MPa.

[0059] The method for preparing 2:17 type samarium cobalt permanent magnets by adding a strong reducing agent to remove oxygen during the smelting process of the samarium cobalt magnets of the present invention is described below with reference to specific embodiments.

[0060] Example 1

[0061] This embodiment provides a method for preparing 2:17 type samarium cobalt permanent magnets by adding a strong reducing agent to remove oxygen during the smelting process of samarium cobalt magnets. Figure 1 shown.

[0062] The metal raw materials are calculated by mass percentage as follows: samarium 25.97wt / %, cobalt 39.66wt / %, iron 26.93wt / %, copper 4.78wt / %, zirconium 2.66wt / %; the total mass is 200g; and the initial O content is 150ppm.

[0063] The specific preparation process is as follows:

[0064] Step 1, cut the material longer than 6cm into pieces, place it in a vacuum induction furnace in the form of cobalt, zirconium, iron, samarium, and copper from bottom to top and loose on the top and tight on the bottom, close the furnace door and evacuate, the vacuum reaches 3.0Pa, start to increase the power to 5kW to preheat the material, keep the vacuum pump on, when the material turns slightly red, turn off the vacuum pump and introduce argon until the meter reaches 60kPa, then increase the power to 25kW and melt for 20min, add a strong reducing agent Ca to the liquid metal melted at high temperature, the amount of Ca added is 0.2g, and melt along with samarium, cobalt, iron and other elements; finally increase the power to 35kW for rapid mixing and stirring;

[0065] Step 2: Turn off the power and let the smelted liquid alloy stand in the smelting furnace. There will be a small amount of solid floating matter, which will be removed and poured into a water-cooled copper mold;

[0066] The oxygen content was tested by nitrogen oxygen analyzer, and the oxygen content was 30ppm. The calcium content was tested by ICP and was 160ppm.

[0067] Step 3: Place the cooled ingot into a crusher, isolate it from oxygen during the whole process, and then place it into a jet mill for fine crushing. The average particle size of the finely crushed powder is 5um.

[0068] Step 4: The prepared powder is compacted in a magnetic field forming press under a magnetic field of 2.0 T, and then cold isostatically compacted under a pressure of 200 MPa.

[0069] Step 5: The pressed sample is placed in a vacuum high-pressure sintering furnace for sintering at a sintering temperature of 1220° C., a sintering pressure of 5 MPa, and a sintering time of 1 h.

[0070] Step 6: The sintered sample is solution treated at a temperature of 1160°C for 2 h, and then quenched.

[0071] Step 7: Aging is performed in a stepwise cooling manner: aging at 800°C for 4 hours, then cooling to 400°C at 1°C / min, keeping at that temperature for 8 hours, and then cooling to room temperature with the furnace to obtain a samarium cobalt permanent magnet.

[0072] After testing, the samarium cobalt permanent magnet prepared by the method has the following characteristics: remanence Br=11.84 kGs, magnetic energy product (BH) m=33.15 MGOe, intrinsic coercive force Hcj=27.66 kOe, and bending strength 200 MPa.

[0073] Embodiments 2 to 7

[0074] This embodiment provides a method for preparing 2:17 type samarium cobalt permanent magnets by adding a strong reducing agent to remove oxygen during the smelting process of samarium cobalt magnets.

[0075] The composition and total mass of the metal raw materials are the same as those in Example 1.

[0076] The order of placing metal raw materials in the vacuum induction furnace from bottom to top is:

[0077] Example 2: zirconium, cobalt, iron, copper, samarium;

[0078] Example 3-4: cobalt, zirconium, iron, samarium, copper;

[0079] Examples 5-7: zirconium, cobalt, iron, copper, samarium.

[0080] The specific preparation steps are the same as those in Example 1, and the different process parameters of the preparation process are shown in Table 1.

[0081] The oxygen and calcium contents in the liquid alloy after smelting in step 2 are shown in Table 2.

[0082] The process parameters of sintering and heat treatment are shown in Table 3.

[0083] The magnetization test and mechanical properties of the prepared samarium cobalt permanent magnet are shown in Table 4.

[0084] Comparative Example 1

[0085] This embodiment provides a method for preparing a samarium cobalt permanent magnet.

[0086] The composition, total mass and placement order of the metal raw materials in the vacuum induction furnace are the same as those in Example 1.

[0087] The preparation process is basically the same as that of Example 1, except that no reducing agent is added during the smelting process. The specific process parameters are shown in Table 1.

[0088] The oxygen and calcium contents in the liquid alloy after smelting are shown in Table 2.

[0089] The process parameters of sintering and heat treatment are shown in Table 3.

[0090] The magnetization test and mechanical properties of the prepared samarium cobalt permanent magnet are shown in Table 4.

[0091] Comparative Example 2

[0092] This embodiment provides a method for preparing a samarium cobalt permanent magnet.

[0093] The composition, total mass and placement order of the metal raw materials in the vacuum induction furnace are the same as those in Example 1.

[0094] The preparation process is basically the same as that of Example 1, except that an excess reducing agent is added. The specific process parameters are shown in Table 1.

[0095] The oxygen and calcium contents in the liquid alloy after smelting are shown in Table 2.

[0096] The process parameters of sintering and heat treatment are shown in Table 3.

[0097] The magnetization test and mechanical properties of the prepared samarium cobalt permanent magnet are shown in Table 4.

[0098] Comparative Example 3

[0099] This embodiment provides a method for preparing a samarium cobalt permanent magnet.

[0100] The composition, total mass and placement order of the metal raw materials in the vacuum induction furnace are the same as those in Example 1.

[0101] The preparation process is basically the same as that of Example 1, except that the reducing agent and the metal raw material are put into the vacuum induction furnace together. The specific process parameters are shown in Table 1.

[0102] The oxygen and calcium contents in the liquid alloy after smelting are shown in Table 2.

[0103] The process parameters of sintering and heat treatment are shown in Table 3.

[0104] The magnetization test and mechanical properties of the prepared samarium cobalt permanent magnet are shown in Table 4.

[0105] Comparative Example 4

[0106] This embodiment provides a method for preparing a samarium cobalt permanent magnet.

[0107] The composition, total mass and placement order of the metal raw materials in the vacuum induction furnace are the same as those in Example 1.

[0108] The preparation process is basically the same as that of Example 1, except that the metal raw materials other than samarium are first added to the vacuum induction furnace, and samarium and the reducing agent are added to the induction furnace together. The specific process parameters are shown in Table 1.

[0109] The oxygen and calcium contents in the liquid alloy after smelting are shown in Table 2.

[0110] The process parameters of sintering and heat treatment are shown in Table 3.

[0111] The magnetization test and mechanical properties of the prepared samarium cobalt permanent magnet are shown in Table 4.

[0112] Comparative Example 5

[0113] This embodiment provides a method for preparing a samarium cobalt permanent magnet.

[0114] The composition, total mass and placement order of the metal raw materials in the vacuum induction furnace are the same as those in Example 1.

[0115] The preparation process is basically the same as that in Example 1, and the specific process parameters are shown in Table 1.

[0116] The difference is that the sintering pressure is 150 MPa, and the process parameters of sintering and heat treatment are as described in Table 3.

[0117] The oxygen and calcium contents in the liquid alloy after smelting are shown in Table 2.

[0118] The magnetization test and mechanical properties of the prepared samarium cobalt permanent magnet are shown in Table 4.

[0119] Comparative Example 6

[0120] This embodiment provides a method for preparing a samarium cobalt permanent magnet.

[0121] The composition, total mass and placement order of the metal raw materials in the vacuum induction furnace are the same as those in Example 1.

[0122] The preparation process is basically the same as that of Example 1, and the specific process parameters are shown in Table 1.

[0123] The difference is that the aging is not divided into stages (after keeping at 800℃ for 1h, it is directly cooled with the furnace). The process parameters of sintering and heat treatment process are described in Table 3.

[0124] The oxygen and calcium contents in the liquid alloy after smelting are shown in Table 2.

[0125] The magnetization test and mechanical properties of the prepared samarium cobalt permanent magnet are shown in Table 4.

[0126] Comparative Example 7

[0127] This embodiment provides a method for preparing a samarium cobalt permanent magnet.

[0128] The composition, total mass and order of placing the metal raw materials in the vacuum induction furnace are the same as those in Example 1. The preparation process is basically the same as that in Example 1, and the specific process parameters are shown in Table 1.

[0129] The difference is that no quenching is performed during the heat treatment process.

[0130] The oxygen and calcium contents in the liquid alloy after smelting are shown in Table 2.

[0131] The magnetization test and mechanical properties of the prepared samarium cobalt permanent magnet are shown in Table 4.

[0132] Comparative Example 8

[0133] This embodiment provides a method for preparing a samarium cobalt permanent magnet.

[0134] The composition, total mass and order of placing the metal raw materials in the vacuum induction furnace are the same as those in Example 1. The preparation process is basically the same as that in Example 1, and the specific process parameters are shown in Table 1.

[0135] The difference is that the cooling method in the second stage aging process is rapid air cooling.

[0136] The oxygen and calcium contents in the liquid alloy after smelting are shown in Table 2.

[0137] The magnetization test and mechanical properties of the prepared samarium cobalt permanent magnet are shown in Table 4.

[0138] Table 1 Process parameters of the preparation process of samarium cobalt permanent magnets in the embodiments of the present invention and the comparative examples

[0139]

[0140]

[0141] Table 2 Oxygen and calcium contents in the liquid alloy after smelting in the embodiments of the present invention and the comparative examples

[0142] serial number Oxygen content ppm Reducing agent content ppm Samarium recovery rate Example 1 30 160 97％ Example 2 40 140 97％ Example 3 50 100 97％ Example 4 40 100 97％ Example 5 50 140 97％ Example 6 30 140 97％ Example 7 35 146 97％ Comparative Example 1 150 / 60％ Comparative Example 2 30 300 97％ Comparative Example 3 30 280 97％ Comparative Example 4 30 150 60％ Comparative Example 5 30 160 97％ Comparative Example 6 30 160 97％ Comparative Example 7 30 160 97％ Comparative Example 8 30 160 97％

[0143] Table 3 Sintering and heat treatment process parameters of the embodiments of the present invention and the comparative examples

[0144]

[0145]

[0146]

[0147] Table 4 Performance parameters of samarium cobalt permanent magnets prepared in the embodiments of the present invention and the comparative examples

[0148]

[0149]

[0150] It can be seen from Tables 1 and 2 that the timing and amount of adding the reducing agent as well as the sintering and heat treatment parameters of Examples 1 to 7 all meet the requirements of the present invention. It can be seen from Table 4 that the magnetic properties and mechanical properties of the permanent magnets prepared in Examples 1 to 7 all reach a relatively high level.

[0151] It can be seen from Table 3 that, compared with Example 1, since no reducing agent is added during smelting, the O content in the liquid alloy is high and the samarium recovery rate is low in Comparative Example 1; compared with Example 1, since excessive reducing agent is added during the smelting process in Comparative Example 2, although the O content in the liquid alloy is low, the residual reducing agent amount is high; compared with Example 1, the reducing agent is added before smelting in Comparative Example 3, resulting in excessive incorporation of Ca into the liquid alloy; compared with Example 1, metallic samarium is added together with calcium during the smelting process in Comparative Example 4, resulting in increased samarium burnout and low recovery rate.

[0152] It can be seen from Table 4 that compared with Example 1, Comparative Example 1 has a poor deoxidation effect, which causes the Sm2O3 particles to hinder the formation of the 1:3R phase and the chemical redistribution of the magnet, thereby deteriorating the magnetic properties; Compared with Example 1, Comparative Example 2 and Comparative Example 3 have excessive residual Ca in the alloy, which reduces the magnetic properties of the magnet and increases the brittleness of the magnet; Compared with Example 1, Comparative Example 4 has excessive samarium loss, which causes the magnetic properties of the magnet to deteriorate; Compared with Example 1, Comparative Examples 5 to 8 have different degrees of reduction in magnetic properties and mechanical properties of the magnet due to the sintering pressure and heat treatment process parameters exceeding the scope of the present invention.

[0153] In summary, the present invention reduces the oxygen content in the liquid alloy to below 50 ppm by adding a strong reducing agent to deoxidize during the smelting process and optimizing the order of adding the metal raw material and the reducing agent, thereby reducing the oxidation of Sm during the smelting process, and the content of the strong reducing agent in the samarium cobalt magnet is less than 200 ppm; by optimizing the sintering and heat treatment process parameters, the magnetic properties of the prepared samarium cobalt permanent magnet meet the requirements of remanence ≥11 kGs, magnetic energy product ≥29 MGOe, intrinsic coercive force ≥25 kOe, and bending strength ≥180 MPa.

[0154] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a 2:17 type samarium cobalt permanent magnet, characterized in that: A vacuum induction furnace is used to melt metal raw materials composed of various single substances. When the metal raw materials are melted by 70% to 100%, a strong reducing agent is added to obtain a liquid alloy along with the melting of the metal raw materials. The liquid alloy is poured, powdered and pressed to obtain a permanent magnet blank. The permanent magnet blank is sintered at a slightly high pressure and then heat treated to obtain a samarium cobalt permanent magnet.

2. The method according to claim 1, characterized in that The strong reducing agent is any one of K, Ca, Na, Mg, Sr, Ba, La, Ce, and Al, or a mixture of multiple thereof.

3. The method according to claim 2, characterized in that The weight ratio of the added amount of the strong reducing agent to the ingredients of the samarium cobalt magnet is 0.0001:1 to 0.01:

1.

4. The method according to claim 1, characterized in that The arrangement order of the metal raw materials in vacuum induction melting is cobalt, zirconium, iron, samarium, copper or zirconium, cobalt, iron, copper, samarium from bottom to top, and the metal raw materials are arranged in a loose upper and tight lower manner.

5. The method according to claim 4, characterized in that The smelting process is as follows: continuously evacuate the material, and after the vacuum degree reaches 0.3-3Pa, bake the material with a baking power of 1-15kW for 1-10min, and maintain vacuum during baking; after baking, stop evacuating the material, introduce argon to 60kPa, increase the power to 20-30kW, and smelt for 10-30min; finally, increase the power to 30-40kW again for rapid mixing and stirring, and the stirring time is 0-10min.

6. The method according to claim 1, characterized in that The pouring process is as follows: the power of the vacuum induction melting furnace is adjusted to 0, the smelted liquid alloy is allowed to stand in the melting furnace for a certain period of time, the slag is removed to remove the solid floating matter, and then the alloy ingot is poured into a water-cooled mold, and then the alloy ingot is obtained after cooling.

7. The method according to claim 1, characterized in that The powder making process is as follows: the whole powder making process is carried out in an oxygen-free environment, the ingot is placed in a crusher for coarse crushing, and then placed in a jet mill for fine crushing to obtain fine powder, wherein the average particle size of the fine powder is 3 to 5 μm; And / or, the pressing process is: compacting the prepared powder in a magnetic field forming press under a magnetic field of 2.0 T, and then performing cold isostatic compaction under a pressure of 200 MPa.

8. The method according to claim 1, characterized in that The sintering process comprises: placing the pressed sample into a vacuum high-pressure sintering furnace for sintering, the sintering temperature is 1200° C. to 1230° C., the sintering pressure is 0 to 5 MPa, and the sintering time is 0.5 h to 2 h.

9. The method according to claim 1, characterized in that: The heat treatment process includes solution treatment-quenching-aging.

10. The method according to claim 9, characterized in that The solution temperature is 1150-1200°C, the time is 2h-10h, and quenching treatment is performed; the aging adopts a staged cooling method, aging at 800-850°C for 20min-10h, cooling at a rate of 0.1-10°C / min, cooling to 300°C-400°C, keeping warm for 1h-20h, and cooling to room temperature with the furnace to obtain a samarium cobalt permanent magnet.

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