JP4868182B2 - Sm-R-T-B (-M) sintered magnet - Google Patents

Description

  The present invention relates to an Sm-R-T-B (-M) based sintered magnet.

  Rare earth sintered magnets are used in various applications because of their excellent magnetic properties and economy, and are indispensable materials in electrical and electronic equipment, the automobile industry, and the like. In addition, the application is expanding more and more due to the recent rise in oil prices and global warming countermeasures.

  There are two types of rare-earth sintered magnets, Sm-Co-based sintered magnets and RTB-based sintered magnets, which are properly used in consideration of their characteristics and cost.

  Sm—Co based sintered magnets are characterized by good temperature characteristics, and are mainly used for applications in high temperature environments. However, since it is a sintered magnet using a lot of expensive Co, there is a problem that the cost increases.

  R-T-B based sintered magnets are rich in Nd, which is the main element, than Sm, and because expensive Co is not used much, raw material costs are lower than Sm-Co based sintered magnets, and magnetic characteristics are also low. Due to its high price, its use continues to expand.

  However, the rare earth sintered magnet as described above is not universal. For example, it can be applied to a low coercivity magnet having good remagnetization characteristics as used in Patent Document 1 (Japanese Patent Laid-Open No. 2006-280195). Can not. This is because it is difficult to produce a product having a coercive force of less than 500 kA / m with a conventional rare earth sintered magnet. Although it is possible to reduce the coercive force itself by adding a large amount of impurities such as carbon, the mass production characteristics of the product are not stable, and the squareness deteriorates, so that the magnetization characteristics deteriorate.

JP 2006-280195 A

  The present invention has been made in view of such circumstances, and an object thereof is to provide a rare earth sintered magnet having good remagnetization characteristics.

As a result of intensive studies to achieve the above object, the present inventors have reached the present invention. The present invention provides an RTB (-M) based sintered magnet [however, 22 to 37]. Mass% R (R is one or a combination of two or more rare earth elements including Y except Sm), 0.5 to 1.5 mass% B, 0 to 4.0 mass% addition Element M (M is Ga, Zr, Nb, Hf, Ta, W, Mo, Al, Si, V, Cr, Ti, Cu, Ag, Mn, Ni, Ge, Sn, Bi, Pb, Zn, C, 1 or a combination of two or more of N and O), the balance being T (T is Fe, or Fe and Co), and a rare earth sintered magnet having a composition of Sm of less than 0.1% by mass. ] Is obtained by diffusing Sm into the magnet from the surface using Sm ₂ O ₃ powder. Sm, R (R is a combination of one or more of the rare earth elements including Y, excluding Sm) ), T (T is Fe or Fe and Co), and B as main components, Sm is 0.1 to 10% by mass, R is 22 to 37% by mass, and B is 0.5 to 1.5% by mass. %, Additive element M (M is Ga, Zr, Nb, Hf, Ta, W, Mo, Al, Si, V, Cr, Ti, Cu, Ag, Mn, Ni, Ge, Sn, Bi, Pb, Zn Sm-R-T-B (-M) based sintered magnet comprising 0 to 4.0% by mass, the balance being T and inevitable impurities. provide. In this case, Hcj (coercive force) is preferably 80 to 500 kA / m, and Br (residual magnetic flux density) is preferably 1 T or more. After full magnetization, the remagnetization factor in a magnetic field of 600 kA / m or less is It is preferably 90% or more.

  The Sm-R-T-B (-M) sintered magnet of the present invention is excellent in remagnetization characteristics, and the sintered magnet according to the present invention is used for applications such as repeated magnetization, demagnetization, and remagnetization. Can be used.

  The Sm-R-T-B (-M) sintered magnet of the present invention is 0.1 to 10% by mass of Sm, 22 to 37% by mass of R (R is a rare earth element including Y except for Sm). 1 or a combination of two or more thereof), 0.5 to 1.5 mass% B, 0 to 4.0 mass% additive element M (M is Ga, Zr, Nb, Hf, Ta, W) , Mo, Al, Si, V, Cr, Ti, Cu, Ag, Mn, Ni, Ge, Sn, Bi, Pb, Zn, C, N, O or a combination of two or more thereof), the balance is A rare earth sintered magnet having a composition composed of T (T is Fe, or Fe and Co).

  Sm is an essential element for improving the remagnetization characteristics. If it is less than 0.1% by mass, the re-magnetization characteristics are poor. Moreover, since coercive force will fall if it exceeds 10 mass%, it is unpreferable.

If the amount of R is less than 22% by mass, the coercive force is likely to be remarkably reduced. On the other hand, if it exceeds 37% by mass, the amount of R-rich phase increases more than necessary, resulting in low residual magnetization, resulting in magnetic Characteristics are degraded.
In this case, R preferably includes Nd, Pr, Dy, Tb, and Ho.

If the amount of B is less than 0.5% by mass, the coercive force is remarkably reduced due to the precipitation of the Nd ₂ Fe ₁₇ phase, and if it exceeds 1.5% by mass, the amount of B-rich phase increases and the residual magnetization is low. turn into.

  The additive element M is used for the purpose of increasing the coercive force or expanding the heat treatment conditions during production, and the kind, amount and combination of the additive elements can be determined as necessary. However, if it exceeds 4.0% by mass, there is a high possibility that the residual magnetization will be remarkably reduced. In addition, it is preferable that content of M is 0.1-3.0 mass%, More preferably, it is 0.2-2.0 mass%.

T is Fe, or Fe and Co. Since Co is a high-priced metal, the amount of addition is desired to be reduced. However, if the temperature of the environment in which the magnet is used is high, the necessary amount is added corresponding to the temperature.
In addition, it is preferable that content of T is 50-72 mass%, More preferably, it is 60-70 mass%. In this case, the Co content is 5% by mass or less, particularly 3% by mass or less of the entire T.

  The rare earth alloy may contain impurities inevitable in production in addition to the above elements.

  The manufacturing method may be performed using the same steps as those of the Sm—Co based sintered magnet and the RTB based sintered magnet, and is not particularly limited, but an example thereof is shown below.

  In the production of a raw material alloy, an ingot, a strip cast, etc. are weighed, melted and cast so as to have a predetermined composition in a vacuum or an inert gas atmosphere. The raw material alloy may be one type or two types (= 2 alloy method).

The pulverization is performed after coarse pulverization. The coarse pulverization may be performed by mechanical pulverization such as a jaw crusher or a brown mill, or pulverization using hydrogen embrittlement, or a combination thereof. The fine pulverization is generally carried out using a jet mill under conditions such that the mass median diameter D ₅₀ in the air flow dispersion type laser diffraction method is 2 to 10 μm.

  The molding is preferably performed in a magnetic field in order to obtain fine residual magnetization by orienting the finely pulverized particles. A parallel magnetic field forming method, a vertical magnetic field forming method, a RIP method, or the like may be performed depending on the required shape and characteristics of the magnet.

Sintering is performed in vacuum or in an inert gas at a temperature such that the density is 7.3 to 7.7 g / cm ³ . The normal sintering temperature is 1,000 to 1,150 ° C.

  Heat treatment can be performed to adjust the coercivity after sintering. This may or may not be done multiple times depending on the required coercivity.

  As another method, the magnet of the present invention can be obtained by a so-called grain boundary diffusion method in which Sm is diffused from the surface of the magnet body to the inside of the magnet after the Sm composition of the sintered magnet is less than 0.1% by mass. It can be produced. In this case, since Sm hardly enters the main phase and is localized only near the grain boundary, the total amount of Sm can be reduced. This makes it possible to produce a magnet having a high Br.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to the following Example.

[ Reference Example 1]
Using Sm, Fe, Co, Al, Cu having a purity of 99.9% or more as a raw material and Nd having a purity of 99.5% or more, a composition formula of 3.0Sm-30.0Nd-64.7Fe-1.0Co- 1.0B-0.2Al-0.1Cu (each mass%) is weighed so as to have a composition, melted in a high-frequency melting furnace, and cast by a strip cast method, with an average thickness of about 0.3 mm. A raw material alloy was produced. The raw material alloy thus produced was subjected to hydrogen storage treatment for 4 hours, and then subjected to dehydrogenation treatment by heating in vacuum at 500 ° C. for 8 hours to perform coarse pulverization. Next, using a jet mill in a nitrogen atmosphere, fine pulverization was performed so that the mass median diameter D ₅₀ was 5.2 μm. The obtained fine powder was pressure-molded at a pressure of 0.5 ton / cm ² while being oriented in a magnetic field of 15 kOe. Next, this compact was sintered in an Ar25 kPa atmosphere at 1,120 ° C. for 3 hours, and further subjected to aging heat treatment at 600 ° C. for 2 hours, thereby producing an Sm—R—T—B system sintered magnet.

[Comparative Example 1]
Using Sm, Co, Fe, Cu, Zr with a purity of 99.9% or more as a raw material, the composition formula 25.7Sm-48.0Co-19.5Fe-4.0Cu-2.8Zr (each mass%) A raw material alloy having an average thickness of about 0.3 mm was prepared by weighing to a composition, melting in a high-frequency melting furnace, and casting by a strip casting method. The produced raw material alloy was coarsely pulverized by a jaw crusher and a brown mill. Next, using a jet mill in a nitrogen atmosphere, fine pulverization was performed so that the mass median diameter D ₅₀ was 5.5 μm. The obtained fine powder was pressure-molded at a pressure of 1.5 ton / cm ² while being oriented in a magnetic field of 15 kOe. Next, this compact was sintered at 1,190 ° C. for 2 hours in an Ar 25 kPa atmosphere, further subjected to a solution treatment for 1 hour at 1,160 ° C. in an Ar atmosphere, and an aging heat treatment for 5 hours at 800 ° C. A system sintered magnet was produced.

[Comparative Example 2]
Using Nd with a purity of 99.5% or more as a raw material and Fe, Co, Al, Cu, Zr with a purity of 99.9% or more, a composition formula 34.0Nd-63.5Fe-1.0Co-1.0B- It is weighed so as to have a composition of 0.2Al-0.2Cu-0.1Zr (each mass%), melted in a high-frequency melting furnace, and cast by a strip cast method. A raw material alloy was produced. The produced raw material alloy was coarsely pulverized by a jaw crusher and a brown mill. Stearic acid as a lubricant was added and mixed at a rate of 0.20% by mass with respect to the obtained coarse powder. Next, using a jet mill in a nitrogen atmosphere, fine pulverization was performed so that the mass median diameter D ₅₀ was 5.2 μm. The obtained fine powder was pressure-molded at a pressure of 0.5 ton / cm ² while being oriented in a magnetic field of 15 kOe. Next, this compact was sintered at 1,080 ° C. for 3 hours in an Ar 25 kPa atmosphere to produce an RTB-based sintered magnet.

Table 1 shows the magnetic properties and re-magnetization properties of the obtained magnets. The re-magnetization characteristics are as follows: each sintered magnet is fully magnetized at 2,000 kA / m, the flux value on the magnet surface is measured, and then the flux is re-magnetized with a predetermined magnetic field in the opposite direction. The percentage of values was evaluated. The re-magnetization rate 1 is 400 kA / m, and the re-magnetization rate 2 is the result when re-magnetization is performed at 600 kA / m. Magnetization and re-magnetization were performed in a closed magnetic circuit. The remagnetization rate of the sintered magnet of Reference Example 1 of the present invention was the highest.

[ Reference Example 2]
Using Sm, Fe, Co, Al, Cu having a purity of 99.9% or more as a raw material and Nd having a purity of 99.5% or more, a composition formula of 0.0 to 12.0 Sm-31.5 Nd-66.2 Weighed so that the composition of 54.2Fe-1.0Co-1.0B-0.2Al-0.1Cu (each mass%) was obtained, and then a sintered magnet was produced in the same manner as in Reference Example 1.

Table 2 shows the magnetic properties and re-magnetization properties of the magnets obtained. Similar to Reference Example 1, the remagnetization characteristics are the results when remagnetization is performed at a remagnetization factor of 1 at 400 kA / m and a remagnetization factor of 2 at 600 kA / m. It can be seen that the remagnetization rate is improved by increasing the amount of Sm. However, when the amount exceeds 10% by mass, the amount of decrease in Hcj increases.

[Example 1 ]
By using Fe, Co, Al, Cu, Zr having a purity of 99.9% or more as a raw material and Nd having a purity of 99.5% or more, a composition formula 33.0Nd-62.6Fe-3.0Co-1.0B- Weighed so that the composition was 0.2Al-0.1Cu-0.1Zr (each mass%), and then a sintered magnet was produced in the same manner as in Reference Example 1. The obtained sintered magnet was cut into a thickness of 3 mm. On the other hand, a slurry was prepared by mixing Sm ₂ O ₃ powder having a mass median diameter D ₅₀ of 100 nm with ethanol at a mass ratio of 50%. The magnet was dipped in the slurry for 30 seconds and pulled up, and then immediately dried with hot air. The Sm ₂ O ₃ powder was put on the surface of the magnet and put into the furnace, and heat treatment (diffusion treatment) was performed at 800 ° C. for 5 hours. The Sm concentration in the sintered magnet after the diffusion treatment was 0.2% by mass.

Table 3 shows the magnetic properties and remagnetization properties of the obtained magnets. Similar to Reference Examples 1 and 2, the remagnetization characteristics are the results when remagnetization is performed at a remagnetization factor of 1 at 400 kA / m and a remagnetization factor of 2 at 600 kA / m. It can be seen that the remagnetization rate is improved by performing the diffusion process of Sm. In addition, it is a good sintered magnet that has both low Br due to Sm diffusion and high Br and high remagnetization characteristics.

Claims (3)

R-T-B (-M) -based sintered magnet [provided that 22 to 37% by mass of R (R is one or a combination of two or more of rare earth elements including Y except Sm); 5 to 1.5 mass% B, 0 to 4.0 mass% additive element M (M is Ga, Zr, Nb, Hf, Ta, W, Mo, Al, Si, V, Cr, Ti, Cu , Ag, Mn, Ni, Ge, Sn, Bi, Pb, Zn, C, N, O, or a combination of two or more), and the balance is T (T is Fe, or Fe and Co) , Sm is a rare earth sintered magnet having a composition of less than 0.1% by mass. ] Is obtained by diffusing Sm into the magnet from the surface using Sm ₂ O ₃ powder. Sm, R (R is a combination of one or more of the rare earth elements including Y, excluding Sm) ), T (T is Fe or Fe and Co), and B as main components, Sm is 0.1 to 10% by mass, R is 22 to 37% by mass, and B is 0.5 to 1.5% by mass. %, Additive element M (M is Ga, Zr, Nb, Hf, Ta, W, Mo, Al, Si, V, Cr, Ti, Cu, Ag, Mn, Ni, Ge, Sn, Bi, Pb, Zn Sm-R-T-B (-M) based sintered magnet comprising 0 to 4.0% by mass, the balance being T and inevitable impurities.   The Sm-R-T-B (-M) sintered magnet according to claim 1, wherein Hcj (coercive force) is 80 to 500 kA / m and Br (residual magnetic flux density) is 1 T or more.   3. The Sm-R-T-B (-M) sintered magnet according to claim 1 or 2, wherein a re-magnetization factor in a magnetic field of 600 kA / m or less is 90% or more after full magnetization.