JP2018082147A - METHOD FOR MANUFACTURING R-Fe-B BASED SINTERED MAGNET - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an R-Fe-B based sintered magnet having good production efficiency and being capable of suppressing a decrease in residual magnetism.SOLUTION: A method for manufacturing an R-Fe-B based sintered magnet includes the steps of: preparing the R-Fe-B based sintered magnet as a matrix; arranging a heavy rare earth RHX containing at least one of metal dysprosium, hydrogenation dysprosium, terbium, and hydrogenation terbium on a surface of the matrix and arranging an RLF layer containing at least one of praseodymium fluoride, neodymium fluoride, praseodymium oxide, and neodymium oxide on an RHX layer; and diffusing heavy rare earth RXE into an inside of the magnet via the surface of the matrix by performing heat treatment in a diffusion furnace.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an R—Fe—B 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 field of new energy vehicles is increasing, and the operating temperature of motors in new energy vehicles is also getting higher, so higher maintenance is required. Magnetic magnets are required, but increasing the coercive force requires the use of a large amount of heavy rare earth elements, which greatly increases the cost of the magnet, 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 is lowered. New energy vehicles are required to have high coercivity and high magnetic energy products, so how to reduce the amount of heavy rare earth elements used to produce magnets with high coercivity and high magnetic energy products However, it was the focus of research on neodymium / iron / boron permanent magnet materials. In recent years, some major companies in Japan and overseas that produce neodymium, iron and boron permanent magnets produce magnets with high coercive force and high magnetic energy product while reducing the amount of heavy rare earths used mainly by two methods. doing. One is a crystal grain refinement technique, and the other is a method of diffusing heavy rare earths at grain boundaries. However, in terms of reducing the amount of heavy rare earth used and increasing the coercive force of the magnet, the effect of crystal grain refinement technology is limited. Since the coercive force can be greatly increased on the assumption that there is almost no decrease or little decrease, using a method in which heavy rare earths are grain boundary diffused, while using a very small amount of heavy rare earth elements, Neodymium, iron and 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 techniques currently applied to mass production can be summarized in the following two methods. One is a contact method. First, a layer of heavy rare earth element is provided on the surface of the magnet by vapor deposition, electroplating, coating, etc., and then the heavy rare earth element is made into a grain boundary by diffusion treatment for a long time. It is characterized in that the purpose of diffusion of grain boundaries is realized by intruding along the inside of the magnet (for example, Patent Publication Nos. CN1898757 and CN101158024). The other is the non-contact method, and the most commonly used method is the vacuum evaporation method. However, after the vapor is formed in the heavy rare earth element by heating in a high vacuum state, the vapor of the heavy rare earth element is formed. Is deposited on the surface of the magnet and diffuses inside the magnet (for example, Patent Publication Nos. CN101651038B and CN10137352A). These two methods are the two most commonly used methods in the current production, can be mass-produced, and both can achieve a favorable grain boundary diffusion effect.

  However, the two methods both have some drawbacks during the production process. The contact method is the simplest and most common method in the actual production process, and its advantages are that it is easy to handle, has low requirements for equipment and work clothes, and is easy to achieve mass production. . Similarly, the drawbacks are obvious, and the main thing is that the surface condition of the magnet is easily damaged during actual production, and during diffusion, a large concentration difference is formed in the portion in direct contact with the heavy rare earth element. The entry of the element into the main phase lowers the magnet's remanence, and the heavy rare earth layer on the surface of the magnet falls off due to oxidation during actual production, preventing it from being completely diffused into the magnet. , Heavy rare earths will be wasted. Also, since direct contact between the magnets becomes impossible during heat treatment, if adhesion problems occur due to contact, it will be necessary to increase the partition between the magnets, occupying a large space, and the loading amount Will drop significantly. On the other hand, in the vacuum evaporation method, the magnet and heavy rare earth element are isolated by a member such as a support base and heated to form vapor in the heavy rare earth element, and the vapor diffuses around the magnet and slowly reaches the inside of the magnet. However, if such a method is used, it is necessary to form a support base using a material that does not easily evaporate at a high temperature so that the magnet and the heavy rare earth element are not in direct contact with each other. In addition to greatly increasing the difficulty of placement, the rack occupies a large space and the load is greatly reduced. Further, since the support base is generally made of a high-cost material, the cost of the processing equipment is greatly increased. Also, the vapor concentration when using the evaporation method is difficult to control, so both process monitoring and equipment requirements are high, and the consistency of the magnet after diffusion is slightly inferior compared to the contact method. It will be. Therefore, since these two methods are obviously insufficient in the process of mass production, this patent presents a grain boundary diffusion technique based on a completely new contact method. The advantage of using this method is that when using this patented method to treat the magnet compared to using the conventional contact method, the efficiency is high and the heavy rare earth on the surface of the magnet is not oxidized. It is in the point that it can protect so that the state of this may not be damaged, and can prevent the fall of the residual magnetism of a magnet. Compared to using a non-contact method, this method is more stable and requires less equipment. In addition, when this method is used, the amount of charge and diffusion efficiency can be greatly increased by causing diffusion treatment by direct contact of the magnets, and the cost of work clothes is also extremely high. It can be greatly reduced.

  In order to eliminate the drawbacks existing in the prior art, the present invention provides a method for producing an R—Fe—B based sintered magnet. The technical policy is to prepare at least one RLF layer of praseodymium fluoride, neodymium fluoride, praseodymium oxide, and neodymium oxide in addition to the heavy rare earth RHX layer of the magnet. By using at least one terbium oxide, on the one hand, the RLF layer prevents the magnets from sticking to each other during the heat treatment so that the magnets can be placed in contact with each other and the caul plate is removed. This reduces the difficulty of placement and increases the amount of charge, and prevents the surface heavy rare earth RHX layer from being oxidized. On the other hand, a large amount of praseodymium neodymium element on the surface of the magnet is volatilized. RLF layer that the residual magnetism of the magnet is reduced by forming the layer of heavy rare earth element Therefore, is that to prevent.

  In order to achieve the object of the present invention, the present invention provides a method for producing 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 kinds 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 any one or several of Ti, V, Cr, Co, Ga, Cu, Mn, Si, Al, Zr, W, and Mo, and the content is 0 to 4 wt%. The remaining amount is Fe.

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

  3) Prepare the heavy rare earth RHX layer on the surface of the treated magnet and the RLF layer outside the heavy rare earth RHX layer to form the treated unit. However, the RHX is one kind or a mixture of several kinds 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) The treated unit in 3) is placed in a sintering furnace and subjected to diffusion treatment under vacuum or inert gas protection conditions, with a diffusion temperature of 800 ° C. to 1000 ° C. and a diffusion time of 2 to 50 hours. . After completion of the diffusion, the magnet is subjected to an aging treatment so that the aging temperature is in the range of 450 to 580 ° C. and the aging time is 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 powder, and the particle size of the powder particles is 0.2 μm to 3.5 μm. For RLF, since it is necessary to form an RLF coating layer having a thickness of 1 to 20 μm outside the RHX layer, the particle size of the RLF powder must be controlled between 0.2 μm and 3.5 μm.

  More preferably, the particle size 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 residual magnetism is greatly reduced after diffusion. If the RHX layer is too thin, the increase in the coercive force of the magnet is reduced and the expected effect cannot be achieved. Further, when the RLF layer is too thin, the RHX layer cannot be effectively protected, the purpose of preventing adhesion cannot be achieved, and the amount of increase in the coercive force of the magnet is also reduced.

  Preferably, in the step 3), the processed magnet has a thickness of 1 to 12 mm. During the heat treatment, the heavy rare earth RHX is diffused into the magnet by the grain boundary that has become a liquid phase, so the concentration difference is mainly the driving force in the diffusion process, but the concentration of the heavy rare earth element on the grain boundary with the main phase. If the difference is too large, it will penetrate into the main phase in the same way, and the residual magnetism of the magnet will be significantly reduced, and the surface layer of the magnet will be adjusted by adjusting the temperature and the thickness of the RLF coating layer on the surface of the magnet during processing. Even if the concentration of heavy rare earth is controlled as much as possible, if the concentration difference is low, the driving force becomes small, so that the diffusion process becomes slow. When the thickness of the magnet exceeds 12 mm, it is difficult to realize complete diffusion, and magnetic performance such as irreversibility and perpendicularity of the magnet is deteriorated.

  Preferably, in step 4), the diffusion temperature is set to 850 to 980 ° C. and the diffusion time is set to 5 to 30 hours. If the temperature is lower than 850 ° C., the driving force for diffusion decreases, 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 due to the dissolved grain boundary phase. Also, the magnetic performance of the surface layer and the center becomes uneven. When the temperature is higher than 980 ° C., the portion where the surface of the magnet and the RHX are in contact with each other is easy to form an alloy in a molten state, and the matrix is eroded, and the heavy rare earth element in the RHX enters the crystal at the same time. As a result, the magnetic performance of the magnet also decreases.

Preferably, in step 4), when vacuum treatment 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, an inert gas is used. The pressure is 500 to 12 KPa as argon gas.

  The creation point of the present invention is that the light rare earth element fluoride coating layer RLF is used as a protective layer, and the light rare earth element fluoride coating layer RLF is not reacted with the elements of the heavy rare earth layer, thereby making the elements of the heavy rare earth layer In addition, the RHX layer on the surface of the magnet can be prevented from directly adhering to the magnet surface, and the adhesion of the RHX layer to the inside of the magnet can be prevented in the process of diffusing heavy rare earth elements to the inside of the magnet. Because the heavy rare earth element is too high, the heavy rare earth element enters the main phase and is replaced by the light rare earth element in the main phase, and the light rare earth element volatilizes in large quantities, greatly reducing the magnet's residual magnetism. It is a point that can be prevented. In addition, RLF powder is safe, reliable, excellent in stability, low in price, convenient in production, storage and use. In the actual production process, coating, silkscreen printing, dipping, etc. Therefore, it is only necessary to prepare for the surface of the magnet on which the RHX layer is arranged, so that this method not only greatly reduces the difficulty in arrangement, but also eliminates the partition and frees up a large space. 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 below, but the examples given are only for the purpose of interpreting the present invention and are not intended to limit the scope of the present invention.

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

When the surface of the magnet is washed with an acid solution or deionized water and then dried, a treated magnet M1 is obtained. See Table 2 for components of M1. First, a terbium coating layer is arranged on the surface of the magnet. In this experiment, brush coating is adopted, the thickness of the terbium coating layer is 50 μm, and the outer surface of the terbium coating layer is a mixed coating composed of praseodymium fluoride and neodymium fluoride. The layers are arranged so that the mass ratio of praseodymium fluoride and neodymium fluoride is 1: 5, and the thickness of the coating layer is 7 μm. Place the coated magnet in the container. Place the container in a heat treatment apparatus, set the diffusion temperature to 930 ° C., set the diffusion time to 18 h, and adopt a vacuum treatment at a heat retention stage of 930 ° C. to set the pressure to 5 × 10 ⁻² Pa to 7.8 × 10 ^{− 3} . After the rapid cooling is completed, the temperature is raised to 520 ° C., an aging treatment is performed for 4 hours, and then the magnet M2 is obtained by rapid cooling to room temperature.

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

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

  When the surface of the magnet is washed with an acid solution or deionized water and then dried, a treated magnet M1 is obtained. See Table 3 for components of M1. First, a terbium coating layer is arranged on the surface of the magnet. In this experiment, brush coating is adopted, the thickness of the terbium coating layer is set to 70 μm, and a mixed coating composed of praseodymium fluoride and neodymium fluoride is formed on the outer surface of the terbium coating layer. The layer is coated so that the mass ratio of praseodymium fluoride and neodymium fluoride is 1: 5 and the thickness of the coating layer is 7 μm. Place the coated magnet in the container. Place the container in the heat treatment apparatus, set the diffusion temperature to 930 ° C, set the diffusion time to 18h, and adopt the vacuum treatment at the heat retention stage of 930 ° C, the pressure is 7.8 x 10-3 to 5 x 10-2 Pa And After the rapid cooling is completed, the temperature is raised to 520 ° C., an aging treatment is performed for 4 hours, and then the magnet M3 is obtained by rapid cooling to room temperature.

  Tables 3 and 4 show that when M3 using such a method is compared with M1, the residual magnetic Br is reduced by about 190 Gs and Hcj is increased by 9.92 KOe. It is 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 Tb content increases by 0.08%. Therefore, when the RHX layer is thickened It has been shown that it is necessary to strictly control the thickness of the RHX layer because the coercive force increases and the residual magnetism decreases.

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

  When the surface of the magnet is washed with an acid solution or deionized water and then dried, a treated magnet M1 is obtained. See Table 2 for components of M1. First, a terbium coating layer is arranged on the surface of the magnet. In this experiment, brush coating is adopted, the thickness of the terbium coating layer is 50 μm, and the outer surface of the terbium coating layer is a mixed coating composed of praseodymium fluoride and neodymium fluoride. The layer is coated so that the mass ratio of praseodymium fluoride and neodymium fluoride is 1: 5 and the thickness of the coating layer is 3 μm. Place the coated magnet in the container. Place the container in the heat treatment apparatus, set the diffusion temperature to 930 ° C, set the diffusion time to 18h, and adopt the vacuum treatment at the heat retention stage of 930 ° C, the pressure is 7.8 x 10-3 to 5 x 10-2 Pa And After the rapid cooling is finished, the temperature is raised to 520 ° C., the aging treatment is performed for 4 hours, and then the magnet M4 is obtained by rapid cooling to room temperature.

Tables 5 and 6 show that when M4 using this method is compared with M1, the residual magnetic Br is reduced by about 50 Gs and Hcj is increased by 8.25 KOe. It is shown that Tb is increased by about 0.37 wt%. When M4 is compared with M2, the residual magnetic Br increases by 30 Gs, the coercive force decreases by 1.05 KOe, and the Tb content decreases by 0.05%. Therefore, the thickness of the RLF layer is increased. When the residual magnetism decreases, the coercive force improvement decreases obviously. Mainly, the RLF layer is too thin, the RLF layer is easily oxidized and volatilized, and diffused into the magnet. It has been shown that the thickness of the RHX coating layer must be strictly required because it is caused by a decrease in content.

Claims (6)

A method for producing an R-Fe-B sintered magnet,
1) A R1-Fe-BM sintered magnet is manufactured, where R1 is selected from any one or several of the rare earth elements Nd, Pr, Tb, Dy, Gd, La, and Ho. The content is 26 wt% to 33 wt%, the B content is 0.8 wt% to 1.2 wt%, and M is Ti, V, Cr, Co, Ga, Cu, Mn, Si, Al, Zr. , W, Mo selected from any one or several types, the content is 0 to 4 wt%, the remaining amount is Fe,
2) The sintered magnets are sequentially washed with deionized water, treated with an acid solution, dried, and a treated magnet is obtained;
3) Prepare a heavy rare earth RHX layer on the surface of the treated magnet and an RLF layer outside the heavy rare earth RHX layer to form a treated unit, wherein the RRH is dysprosium, dysprosium hydride, terbium, Any one or a mixture of terbium hydrides, and the RLF is at least one of praseodymium fluoride, neodymium fluoride, praseodymium oxide, neodymium oxide,
4) Place the treated unit in 3) in a sintering furnace and perform diffusion treatment under vacuum or inert gas protection conditions, so that the diffusion temperature is 800 ° C to 1000 ° C and the diffusion time is 2 to 50 hours. , After diffusing, the magnet is subjected to an aging treatment, the aging temperature is in the range of 450 to 580 ° C., and the aging time is 4 to 6 hours,
For producing an R—Fe—B based sintered magnet comprising   In step 3), the RLF form 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, wherein:   2. The method of manufacturing an R—Fe—B based sintered magnet according to claim 1, wherein in the step 3), the thickness of the processed magnet is 1 to 12 mm.   2. 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 h. In step 4), when vacuum treatment 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 KPa. The R- according to claim 2, wherein the powder particles have a particle size of 0.5 to 2.5 µm, the RLF layer has a thickness of 3 to 15 µm, and the RHX layer has a thickness of 10 to 100 µm. Manufacturing method of Fe-B system sintered magnet.