JP6506361B2 - Method of manufacturing R-Fe-B sintered magnet - Google Patents

Description

  The present invention relates to a method of manufacturing an R-Fe-B based sintered magnet and belongs to the field of rare earth permanent magnet materials.

  With the rapid development of new energy vehicles, the demand for permanent magnet motors in the new energy vehicle field is increasing, and the operating temperature of motors in new energy vehicles is also higher, so higher maintenance Although a magnet of magnetic force is required, a large amount of heavy rare earth elements is required to increase the coercivity, so the cost of the magnet will rise sharply, and during melting Even if a large amount of heavy rare earth is directly added to the magnet, the magnetic energy product of the magnet will be reduced. As new energy vehicles are required to have high coercivity and high magnetic energy products, how to reduce the amount of heavy rare earth elements used to produce magnets with high coercivity and high magnetic energy products Was the focus of research on neodymium-iron-boron permanent magnet materials. In recent years, some major domestic and foreign companies that produce neodymium, iron and boron permanent magnets produce magnets with high coercivity and high magnetic energy product while reducing the amount of heavy rare earth used mainly by two methods. doing. One is a grain refining technique, and the other is a method of grain boundary diffusion of heavy rare earth. However, although the effect of grain refining techniques is limited in the effect of reducing the amount of heavy rare earth used to increase the coercive force of the magnet, the method of diffusing heavy rare earth elements at grain boundaries diffuses the residual magnetism of the magnet. Since the coercivity can be greatly enhanced on the premise that the decrease hardly occurs or the decrease hardly occurs, the method of diffusing heavy rare earth at grain boundaries can be used while maintaining a very small amount of heavy rare earth element. Neodymium-iron-boron permanent magnets with high magnetic force and high magnetic energy product can be produced, and ultra-high performance magnets can be produced by grain boundary diffusion technology.

  The grain boundary diffusion technology currently applied to mass production can be roughly summarized into the following two methods. One is the contact method. First, a heavy rare earth element layer is formed on the surface of the magnet by vapor deposition, electroplating, coating, etc. It is characterized in that the purpose of the diffusion of grain boundaries is realized by infiltrating the inside of the magnet along (see, for example, Patent Publication Nos. CN 1898757 and CN 101158024). The other is non-contact method, and vacuum evaporation method is most commonly used at present, but after forming heavy rare earth element vapor by heating under high vacuum condition, vapor of heavy rare earth element Is deposited on the surface of the magnet and diffused inside the magnet (for example, Patent Publication Nos. CN101651038B and CN101375352A). These two methods are the two methods most commonly found in current production, and can be mass-produced, and both can achieve favorable grain boundary diffusion effects.

  However, both methods have some drawbacks in the production process. The contact method is the simplest and most common method in the actual production process, and its advantage is that it is easy to handle, has low requirements for equipment and work clothes, and is easy to achieve mass production . Similarly, its disadvantages are also evident, mainly due to the fact that the state of the surface of the magnet is easily damaged during actual production, and a large concentration difference is formed in the part directly in contact with the heavy rare earth element during diffusion. Elements entering the main phase lower the remanence of the magnet and, during actual production, the heavy rare earth layer on the surface of the magnet is dropped off due to oxidation and can not be completely diffused in the magnet. , Will waste the heavy rare earth. In addition, since the magnet and the magnet can not be in direct contact with each other during the heat treatment, if the problem of adhesion is caused by the contact, it is necessary to increase the partition between the magnets, which occupies a large space, Will drop significantly. On the other hand, the vacuum evaporation method separates the magnet and the heavy rare earth element by a member such as a support and heats the heavy rare earth element to form a vapor, and the vapor is diffused around the magnet to slowly reach the inside of the magnet If the method is used, it is necessary to form a support base using a material that is difficult to evaporate at high temperature in the furnace body so that the magnet and the heavy rare earth element do not come in direct contact with each other. Along with greatly increasing the difficulty in the arrangement, the rack occupies a large space and the loading amount is greatly reduced. Also, since the support is generally made of expensive materials, the cost of the processing equipment will be significantly increased. In addition, since the concentration of steam when using the evaporation method is difficult to control, both the process monitoring and equipment requirements become high, and the consistency of the magnet after diffusion is slightly inferior to the contact method. It will be. Therefore, in these two methods, since there are clearly insufficient points in the mass production process, this patent presents a completely new contact boundary grain diffusion technique by contact method, but this patent method The advantage of using the present invention is that when processing the magnet using this patent method compared to using the conventional contact method, the efficiency is also higher and the heavy rare earth on the surface of the magnet can not be oxidized, the surface of the magnet In order to prevent the loss of the residual magnetism of the magnet, it is possible to prevent the state of Compared to using the non-contact method, this method is more stable and has lower equipment requirements. In addition, using this method, it is possible to extremely increase the charge amount and the diffusion efficiency without causing the problem of adhesion by direct contact of the magnet and diffusion processing, and the cost of the work clothes is also extremely high. It can be greatly reduced.

  In order to solve the drawbacks existing in the prior art, the present invention provides a method of manufacturing an R-Fe-B based sintered magnet. Its technical policy is to provide at least one RLF layer of praseodymium fluoride, neodymium fluoride, praseodymium oxide, neodymium oxide in addition to heavy rare earth RHX layer of magnet, heavy rare earth RHX as dysprosium, dysprosium hydride, terbium, hydrogen By using at least one type of terbium fluoride, on the other hand, the RLF layer allows the magnets to be placed in contact so that the magnets do not adhere to one another during heat treatment, and the backing plate is discharged. While discarding, the difficulty of arrangement is reduced to increase the amount of charge, and the heavy rare earth RHX layer on the surface can be prevented from being oxidized, and on the other hand, a large amount of praseodymium neodymium element volatilizes on the surface of the magnet RLF layer reduces the residual magnetism of the magnet by forming a layer of heavy rare earth elements. Therefore, is that to prevent.

  In order to realize the object of the present invention, the present invention provides a method of manufacturing an R-Fe-B based sintered magnet including the following matters.

  1) Manufacture R1-Fe-BM sintered magnet. However, R1 is selected from any one or several of rare earth elements Nd, Pr, Tb, Dy, Gd, La and Ho, and the content of R1 is 26 wt% to 33 wt%. The content of B is 0.8 wt% to 1.2 wt%. M is selected from one or more of Ti, V, Cr, Co, Ga, Cu, Mn, Si, Al, Zr, W, and Mo, and the content thereof is 0 to 4 wt%. The remaining amount is Fe.

2) The sintered magnet is sequentially washed with an acid solution, washed with deionized water, and dried to obtain a treated magnet.

  3) Apply a heavy rare earth RHX layer to the surface of the treated magnet and a RLF layer outside the heavy rare earth RHX layer to form a treated unit. However, the RHX is one or a mixture of one or more of dysprosium, dysprosium hydride, terbium and terbium hydride. The RLF is at least one of praseodymium fluoride, neodymium fluoride, praseodymium oxide, and neodymium oxide.

  4) Place the treated unit in 3) in a sintering furnace and perform diffusion treatment under vacuum or inert gas protection conditions, and let the diffusion temperature be 800 ° C. to 1000 ° C., and the diffusion time be 2 to 50 hours . After the end of diffusion, the magnet is subjected to an aging treatment, and the aging temperature is in the range of 450 to 580 ° C., and the aging time is set to 4 to 6 hours.

  Preferably, the thickness of the RHX layer is 5 to 200 μm, and the thickness of the RLF layer is 1 to 20 μm. The form of RLF is a powder, and the particle size of the powder particle is 0.2 μm to 3.5 μm. For RLF, the particle size of the RLF powder should be controlled between 0.2 μm and 3.5 μm, as it is necessary to form an RLF coating layer with a thickness of 1 to 20 μm outside the RHX layer.

  More preferably, the particle diameter of the powder particles is 0.5 μm to 2.5 μm, the thickness of the RHX layer is 10 to 100 μm, and the thickness of the RLF layer is 3 to 15 μm. If the RHX layer is too thick, the reduction of the remanence of the magnet after diffusion will be large, and if the RHX layer is too thin, the increase of the coercivity of the magnet will be small and the expected effect can not be achieved. In addition, when the RLF layer is too thin, the RHX layer can not be effectively protected, and the purpose of preventing adhesion can not be achieved, and the amount of increase in the coercive force of the magnet also decreases.

  Preferably, in step 3), the thickness of the processed magnet is 1 to 12 mm. Since the heavy rare earth RHX is diffused to the magnet by the grain boundaries in the liquid phase during the heat treatment, the concentration difference mainly becomes the driving force in the diffusion process, but the concentration of the heavy rare earth element with the main phase on the grain boundaries If the difference is too large, it will intrude into the main phase in the same way and significantly reduce the remanence of the magnet, and by controlling the temperature, the thickness of the RLF coating layer on the surface of the magnet, etc. during processing, the surface layer of the magnet Even if the concentration of heavy rare earth is controlled as much as possible, if the difference in concentration is low, the driving force becomes small, so the diffusion process also becomes slow. If the thickness of the magnet is more than 12 mm, it is difficult to realize complete diffusion, and the magnet performance such as magnet irreversibility and squareness is degraded.

  Preferably, in the step 4), the diffusion temperature is 850 to 980 ° C., and the diffusion time is 5 to 30 hours. If the temperature is lower than 850 ° C., the driving force for diffusion is reduced, and it becomes difficult for the heavy rare earth elements in RHX to reach the inside of the magnet from the surface of the magnet by the grain boundary phase to be melted. The magnetic performance of the surface and center of the core will also be uneven. When the temperature is higher than 980 ° C., the surface of the magnet and the contact point of RHX easily form an alloy in a molten state, which causes the matrix to be eroded, and the heavy rare earth elements in RHX simultaneously enter the crystal. Therefore, the magnetic performance of the magnet will also be degraded.

Preferably, in the step 4), when vacuum processing is selected and used, the vacuum degree is 5 × 10 ⁻¹ to 1 × 10 ⁻⁵ Pa, and when inert gas protection conditions are selected and used, an inert gas is used. The pressure is 500 to 12 KPa as argon gas.

  The point of creation of the present invention is that the element of the heavy rare earth layer is made by using the light rare earth element fluoride coating layer RLF as a protective layer and not reacting the light rare earth element fluoride coating layer RLF with the elements of the heavy rare earth layer. In addition to preventing oxidation, it is possible for the RHX layer on the surface of the magnet not to be in direct contact to cause adhesion, and in the process of diffusing the heavy rare earth element to the inside of the magnet, Because heavy rare earth elements are too high, heavy rare earth elements enter the main phase and are replaced by light rare earth elements in the main phase, and the light rare earth elements volatilize in a large amount, which significantly reduces the remanence of the magnet. The point is that you can prevent it from In addition, RLF powder is safe, reliable, stable, low in price, convenient in production, storage, and use processes, and in the actual production process, methods such as coating, silk screen printing and dipping In such a method, not only the difficulty in the placement is greatly reduced, but also the partition is discarded and a large space is released because such a method is sufficient to be prepared on the surface of the magnet on which the RHX layer is placed. The effective throughput of the diffusion furnace is greatly increased, and the production cost is reduced.

  The principles and features of the present invention will be described in the following, but the listed examples are only for interpreting the present invention, and not for limiting the scope of the present invention.

Example 1
The raw materials placed under inert gas protection are melted using a vacuum melting furnace to form flakes with a thickness of 0.1 to 0.5 mm, and the gold phase grain boundaries of flakes of R-Fe-B alloy Make it clear. The flakes of the alloy are machine-ground and hydrogen-ground, and then crushed by a jet mill to an SMD of 3.4 μm. It is oriented using a magnetic field of 15 KOe, compression molded and compacted to a compact density of 3.95 g / cm ³ . The compacted product is vacuum sintered in a sintering furnace and sintered first at 1080 ° C. for 330 minutes. Thereafter, it is subjected to aging treatment, and aged at 480 ° C. for 240 minutes to obtain a green compact. The green compact is cut into magnets of final product dimensions with a multi-wire, and the dimensions of the magnets are 27 mm * 15 mm * 5 mm, and the tolerance is ± 0.05 mm.

The magnet is washed with an acid solution, deionized water and dried to obtain a treated magnet M1. See Table 2 for the components of M1. First, a terbium coating layer is disposed on the surface of the magnet, and in this experiment, brush coating is employed, the thickness of the terbium coating layer is 50 μm, and the outer surface of the terbium coating layer is a mixed coating consisting of praseodymium fluoride The layers are arranged so that the mass ratio of praseodymium fluoride to neodymium fluoride is 1: 5 and the thickness of the coating layer is 7 μm. Place the coated magnet in a container. The vessel is placed in a heat treatment apparatus, the diffusion temperature set is 930 ° C., the diffusion time is 18 h, and vacuum treatment is employed in the heat retention step of 930 ° C. and the pressure is 5 × 10 ⁻² Pa to 7.8 × 10 ^{− Set} to ³ After quenching is completed, the temperature is raised to 520 ° C. and aging treatment is performed for 4 hours, and then quenching is performed to normal temperature to obtain magnet M2.

  In Tables 1 and 2, when M2 using such a method is compared with M1, the residual magnetic Br decreases by about 80 Gs and Hcj increases by 9.28 KOe, and the component measurement shows that M2 is M1. It is further shown that Tb is increased by about 0.41 wt%.

Example 2
The raw materials placed under inert gas protection are melted using a vacuum melting furnace to form flakes with a thickness of 0.1 to 0.5 mm, and the gold phase grain boundaries of flakes of R-Fe-B alloy Make it clear. The flakes of the alloy are machine-ground and hydrogen-ground, and then crushed by a jet mill to an SMD of 3.4 μm. It is oriented using a magnetic field of 15 KOe, compression molded and compacted to a compact density of 3.95 g / cm ³ . The compacted product is vacuum sintered in a sintering furnace and sintered first at 1080 ° C. for 330 minutes. Thereafter, it is subjected to aging treatment, and aged at 480 ° C. for 240 minutes to obtain a green compact. The green compact is cut into magnets of final product dimensions with a multi-wire, and the dimensions of the magnets are 27 mm * 15 mm * 5 mm, and the tolerance is ± 0.05 mm.

  The magnet is washed with an acid solution, deionized water and dried to obtain a treated magnet M1. See Table 3 for the components of M1. First, a terbium coating layer was placed on the surface of the magnet, and in this experiment a brush coating was employed, the thickness of the terbium coating layer was 70 μm, and the outer surface of the terbium coating layer was a mixed coating consisting of praseodymium fluoride and neodymium fluoride. The layer is coated so that the mass ratio of praseodymium fluoride to neodymium fluoride is 1: 5, and the thickness of the coating layer is 7 μm. Place the coated magnet in a container. The container is placed in a heat treatment apparatus, the diffusion temperature set is 930 ° C., the diffusion time is 18 h, and vacuum treatment is adopted in the heat retention step of 930 ° C. and the pressure is 7.8 × 10 −3 to 5 × 10 −2 Pa I assume. After quenching is completed, the temperature is raised to 520 ° C. and aging treatment is performed for 4 hours, and then quenching is performed to normal temperature to obtain magnet M3.

  In Tables 3 and 4, when M3 using such a method is compared with M1, the residual magnetic Br decreases by about 190 Gs and Hcj increases by 9.92 KOe, and the component measurement shows that M3 is M1. It is further shown that Tb is increased by about 0.49 wt%. When M3 is compared with M2, the residual magnetic Br decreases by 110 Gs, the coercive force Hcj increases by 0.64 KOe, and the content of Tb increases by 0.08%. It has been shown that the thickness of the RHX layer needs to be strictly controlled since the coercivity increases and the remanence decreases too.

Example 3
The raw materials placed under inert gas protection are melted using a vacuum melting furnace to form flakes with a thickness of 0.1 to 0.5 mm and the gold phase boundaries of flakes of R-Fe-B alloy Make it clear. The flakes of the alloy are machine-ground and hydrogen-ground, and then crushed by a jet mill to an SMD of 3.4 μm. It is oriented using a magnetic field of 15 KOe, compression molded and compacted to a compact density of 3.95 g / cm ³ . The compacted product is vacuum sintered in a sintering furnace and sintered first at 1080 ° C. for 330 minutes. Thereafter, it is subjected to aging treatment, and aged at 480 ° C. for 240 minutes to obtain a green compact. The green compact is cut into magnets of final product dimensions with a multi-wire, and the dimensions of the magnets are 27 mm * 15 mm * 5 mm, and the tolerance is ± 0.05 mm.

  The magnet is washed with an acid solution, deionized water and dried to obtain a treated magnet M1. See Table 2 for the components of M1. First, a terbium coating layer is disposed on the surface of the magnet, and in this experiment a brush coating is employed, the thickness of the terbium coating layer is 50 μm, and the outer surface of the terbium coating layer is a mixed coating consisting of praseodymium fluoride and neodymium fluoride. The layer is coated so that the mass ratio of praseodymium fluoride to neodymium fluoride is 1: 5, and the thickness of the coating layer is 3 μm. Place the coated magnet in a container. The container is placed in a heat treatment apparatus, the diffusion temperature set is 930 ° C., the diffusion time is 18 h, and vacuum treatment is adopted in the heat retention step of 930 ° C. and the pressure is 7.8 × 10 −3 to 5 × 10 −2 Pa I assume. After quenching is completed, the temperature is raised to 520 ° C. and aging treatment is performed for 4 hours, and then quenching is performed to normal temperature to obtain magnet M4.

In Tables 5 and 6, when M4 using such a method is compared with M1, the residual magnetic Br decreases by about 50 Gs and Hcj increases by 8.25 KOe, and the component measurement shows that M4 is M1. It is shown that Tb is increased by about 0.37 wt%. When M4 is compared with M2, the remanence Br increases by 30 Gs, the coercivity decreases by 1.05 KOe, and the Tb content decreases by 0.05%, so the thickness of the RLF layer is increased. When the reduction in remanence decreases and the improvement in coercivity also decreases obviously, the RLF layer is mainly too thin, the RLF layer is easily oxidized and volatilized, and it is diffused and enters the magnet. It has been shown that the thickness of the RHX coating layer has to be strictly required, as it is caused by the content reduction.

Claims (6)

A method of manufacturing an R-Fe-B sintered magnet, comprising:
1) R1-Fe-BM sintered magnet is manufactured, provided that R1 is selected from one or more of rare earth elements Nd, Pr, Tb, Dy, Gd, La and Ho, The content is 26 wt% to 33 wt%, the content of B is 0.8 wt% to 1.2 wt%, and M is Ti, V, Cr, Co, Ga, Cu, Mn, Si, Al, Zr And W and Mo, and the content thereof is 0 to 4 wt%, and the remaining amount is Fe,
2) treating the sintered magnet sequentially with an acid solution , washing with deionized water and drying treatment to obtain a treated magnet;
3) Prepare a heavy rare earth RHX layer on the surface of the treated magnet and a RLF layer outside the heavy rare earth RHX layer to form a treated unit, wherein said RHX is dysprosium, dysprosium hydride, terbium, And any one or a mixture of several types of terbium hydride, wherein the RLF is at least one of praseodymium fluoride, neodymium fluoride, praseodymium oxide, and neodymium oxide;
4) The treated unit in 3) is placed in a sintering furnace and diffusion treated under vacuum or inert gas protection conditions to a diffusion temperature of 800 ° C. to 1000 ° C. and a diffusion time of 2 to 50 hours. After the diffusion is complete, the magnet is subjected to aging treatment, the aging temperature is in the range of 450 to 580 ° C., and the aging time is 4 to 6 hours,
Method of producing an R-Fe-B based sintered magnet including   In the step 3), the form of the RLF is powder, the particle size of the powder particles is 0.2 μm to 3.5 μm, the thickness of the RLF layer is 1 to 20 μm, and the thickness of the RHX layer is 5 to 200 μm The method for producing an R-Fe-B based sintered magnet according to claim 1, characterized in that   The method for manufacturing an R-Fe-B based sintered magnet according to claim 1, wherein the thickness of the treated magnet in step 3) is 1 to 12 mm.   The method for producing an R-Fe-B based sintered magnet according to claim 1, wherein the diffusion temperature is 850 to 980 ° C and the diffusion time is 5 to 30 hours. In the step 4), when vacuum processing is selected and used, the degree of vacuum is 5 × 10 −1 to 1 × 10 −5 Pa, and when inert gas protection conditions are selected and used, the inert gas is argon gas, The method for producing an R-Fe-B based sintered magnet according to claim 1, wherein the pressure is 500 to 12 000 Pa. The R- as set forth in claim 2, wherein the particle size of the powder particle is 0.5 μm to 2.5 μm, the thickness of the RLF layer is 3 to 15 μm, and the thickness of the RHX layer is 10 to 100 μm. Method of manufacturing Fe-B based sintered magnet.