R-t-b sintered magnet and method for producing same

Abstract

An R-T-B sintered magnet (R represents a rare earth element containing Nd, and T represents a transition metal element containing Fe) contains at least dysprosium (Dy) as a rare earth element, and when B is the value of saturation remanent magnetization of the R-T-B sintered magnet and A is the value of magnetization when an external magnetic field of 500 kA / m in an initial magnetization curve is applied to the R-T-B sintered magnet, B represents the value of saturation remanent magnetization of the R-T-B sintered magnet, and A represents the value of magnetization when B represents the value of saturation remanent magnetization of the R-T-B sintered magnet. The magnetization ratio is represented by A / B, in this case, the magnetization ratio is less than 1.0 (but greater than 0), and the inter-pole pitch in the R-T-B-based sintered magnet is less than 4 mm (but greater than 0 mm).

Description

Technical Field

[0001] The present invention relates to an RTB-based sintered magnet and a method for manufacturing the same. Background Art

[0002] Conventionally, R (rare earth element R)-T (transition metal element T)-B (boron) permanent magnets have high magnetic properties, and in particular, R (as a rare earth element, it must contain Nd)-T (Fe, etc.)-B sintered magnets have excellent magnetic properties, and are therefore widely used in various electronic devices, home appliances, and motors or actuators mounted on automobiles, etc. R (as a rare earth element, it must contain Nd)-T (Fe, etc.)-B magnets used in motors and actuators, etc., are required to have high coercive force (magnetic retention force) even in high temperature environments because the coercive force of permanent magnets decreases at high temperatures.

[0003] As a method for improving the coercive force of such R (as a rare earth element, Nd must be included)-T (Fe, etc.)-B system sintered magnets, it is known to add dysprosium (Dy) or terbium (Tb) as heavy rare earth elements. For example, Patent Document 1 describes that the coercive force is improved by replacing a part of Nd near the surface of the Nd2Fe14B intermetallic compound as the main phase with Dy and / or Tb.

[0004] The high coercivity of magnets will lead to an increase in the magnetizing magnetic field. That is, in order to fully bring out the magnetizing characteristics of R (Nd must be included as a rare earth element)-T (Fe, etc.)-B system sintered magnets to which dysprosium (Dy) or terbium (Tb) as heavy rare earth elements are added, saturation magnetization is required. For example, it is recorded in Patent Document 2 that in the case of saturation magnetization, the magnetizing magnetic field is generally considered to be 3 to 5 times the coercivity of the magnet as the magnetized object, but in the case of Nd-Fe-B system sintered magnets, since the coercivity generating mechanism is a novel type, it is also considered that the initial magnetizing magnetic field can be small and can be a magnetic field strength of approximately the same magnitude as the coercivity.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Laid-Open No. 6-096928

[0008] Patent Document 2: Japanese Patent Laid-Open No. 5-047558 Summary of the invention

[0009] Problems to be solved by the invention

[0010] However, as described above, among Nd-Fe-B system sintered magnets to which dysprosium (Dy) or terbium (Tb) is added, there are also sintered magnets having a coercive force of 2785 kA / m or more (for example, N32EZ (trade name manufactured by Shin-Etsu Chemical Co., Ltd., sample C described below). When pulse magnetizing such Nd-Fe-B system sintered magnets having a large coercive force, a device for generating a large magnetizing magnetic field of at least about 2800 kA / m or more is required for saturation magnetization. In addition, when the pole pitch is small and multi-pole magnetization is required, the wire diameter of the coil wound on the magnetizing yoke becomes thinner, and there is a problem that a high current for generating the required magnetizing magnetic field cannot flow, and a sufficient magnetizing magnetic field cannot be applied.

[0011] The present invention has been made in view of the above, and an object of the present invention is to provide an RTB based sintered magnet which can perform multi-pole magnetization and increase the generated magnetic field after magnetization even when magnetization is performed with a small pole pitch, and a method for producing the same.

[0012] Technical means of solving problems

[0013] In order to solve the above-mentioned problems and achieve the purpose, one form of the RTB system sintered magnet of the present invention is an RTB system sintered magnet (R represents a rare earth element including Nd, and T represents a transition metal element including Fe), wherein the RTB system sintered magnet contains at least dysprosium (Dy) as a rare earth element, and when the value of the saturation residual magnetization of the RTB system sintered magnet is set to B and the value of the magnetization when an external magnetic field of 500kA / m in the initial magnetization curve is applied to the RTB system sintered magnet is set to A, the magnetization ratio is represented by A / B, in which case the magnetization ratio is less than 1.0 (but greater than 0), and the pole spacing in the RTB system sintered magnet is less than 4mm (but greater than 0mm).

[0014] Effects of the Invention

[0015] According to the aspect of the present invention, the following effects are achieved: an RTB based sintered magnet can be provided which can perform multi-pole magnetization and increase the generated magnetic field after magnetization even when magnetization is performed with a small pole pitch. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [ Figure 1 ] Figure 1 It is a diagram showing a schematic configuration example of a magnetizing device used in the embodiment.

[0017] [ Figure 2 ] Figure 2 This is a schematic perspective view showing a field magnet used in the field magnet section.

[0018] [ Figure 3 ] Figure 3This is a plan view schematically illustrating the inter-pole spacing in a magnetized object.

[0019] [ Figure 4 ] Figure 4 It’s about using Figure 1 The graph shows the relationship between each pole pitch and the magnetization index for each sample after the samples in the embodiment and the comparative example were magnetized by the magnetization device shown.

[0020] [ Figure 5 ] Figure 5 This is a graph showing the relationship between each pole pitch and the magnetization index for each sample after pulse magnetization as a comparative example.

[0021] [ Figure 6 ] Figure 6 This is a graph showing the relationship between the interpolar spacing and the magnetization index in sample C (Example 3).

[0022] [ Figure 7 ] Figure 7 It is a graph showing the first quadrant in the hysteresis curve of each sample. DETAILED DESCRIPTION

[0023] Hereinafter, an RTB based sintered magnet and a method for producing the same according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the above-described embodiment.

[0024] <RTB based sintered magnet according to the embodiment>

[0025] The RTB (boron) magnet constituting the RTB sintered magnet of the embodiment will be described. The RTB magnet constituting the RTB magnet powder contains R2T which is a ternary tetragonal compound. 14 B phase (such as Nd2Fe 14 B-type compound phase) as the main phase. In addition, RTB-based magnets generally also contain an R-rich phase. R represents a rare earth element containing Nd and / or Pr. In other words, R contains Nd and / or Pr as essential components.

[0026] Rare earth elements include, in addition to neodymium (Nd) and praseodymium (Pr), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu). Rare earth elements other than Nd and Pr may be used alone or in combination of two or more.

[0027] Specifically, as R, only Nd may be used, only Pr may be used, or only Nd and Pr may be used. In addition, Nd and rare earth elements other than Nd and Pr may be used, Pr and rare earth elements other than Nd and Pr may be used, or Nd and Pr and rare earth elements other than Nd and Pr may be used. As R, it is preferred to use at least Nd.

[0028] T represents Fe, or Fe and Co. Thus, T may be Fe alone, or may be partially substituted with Co. When the total amount of T is 100 atomic %, Fe is preferably contained in an amount of 50 atomic % or more.

[0029] RTB magnets may also contain other elements. Examples of other elements include titanium, zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W). Other elements may be used alone or in combination of two or more.

[0030] In the RTB-based magnet, R is preferably contained in an amount of 10 atomic % or more and 20 atomic % or less. B is preferably contained in an amount of 6 atomic % or more and 8 atomic % or less. In addition, when the other elements are contained, it is preferred that the other elements are contained in an amount exceeding 0 atomic % and 3 atomic % or less in total. In addition, here, the remainder is the total amount of T and the elements inevitably contained.

[0031] In addition, in the RTB system magnet, it is preferable to contain at least dysprosium (Dy) as a heavy rare earth element. For the Nd-Fe-B system sintered magnet with a large amount of dysprosium (Dy) added to increase the intrinsic coercive force, it is preferable because the generated magnetic field after magnetization can be increased even if the pole pitch is reduced. Therefore, the pole pitch in the RTB system sintered magnet can be set to less than 4mm (but greater than 0mm).

[0032] Furthermore, when the hysteresis curve of the RTB system sintered magnet is measured, when the ratio of the residual magnetization to the saturation magnetization in the initial magnetization curve in the first quadrant is defined as the magnetization ratio, it is preferred that the magnetization ratio is less than 0.5. When the magnetization ratio is less than 0.5, an RTB system sintered magnet that is difficult to magnetize but has a large holding force can be obtained. However, by the manufacturing method described below, an RTB system sintered magnet with a large coercive force can be easily obtained.

[0033] <Method for producing RTB based sintered magnet according to embodiment>

[0034] The manufacturing method of the RTB system sintered magnet of the embodiment includes the step of preparing the RTB system sintered magnet. Then, it includes the magnetization step of magnetizing the magnetized object using a magnetization device, wherein the magnetization device comprises: an excitation part, which uses the prepared RTB system sintered magnet as the magnetized object and arranges a plurality of magnetization permanent magnets at equal intervals to generate a magnetic field for the magnetized object; and a heating part, which has a heating surface facing the magnetized object in the axial direction of the magnetized object and heats the magnetized object.

[0035] In the magnetization process, the magnetized object is arranged on the excitation part, and the magnetized object is heated by the heating part in a manner of heating the object to a temperature higher than the Curie point of the magnetized object and lower than the Curie point of the magnetizing permanent magnet, and then cooling the object to a temperature lower than the Curie point of the magnetized object, and applying a magnetizing magnetic field to the magnetized object by the magnetizing permanent magnet. The temperature lower than the Curie point of the magnetizing permanent magnet may be 800°C or higher, but considering the operation guarantee temperature of the magnetizing device, the ideal temperature is 350°C or lower.

[0036] In the excitation unit, the magnetizing permanent magnets are arranged in such a manner that the pole pitch in the magnetized object after the magnetizing step is less than 4 mm (but greater than 0 mm).

[0037] In the magnetization process, the magnetized object is magnetized by a magnetization device. Figure 1 This is a diagram showing a schematic configuration example of a magnetizing device for performing ultra high magnetizing (UHM) magnetization used in the embodiment.

[0038] like Figure 1 As shown, the magnetizing device 1 includes: a stand 2, a moving part 3, a heating part 4, a preheating part 5, an excitation part 6, a holding member 7, a cooling part 8, and a control part 10. The magnetized object 100 is placed on the preheating part 5 and magnetized to manufacture the magnetized object (magnetized object after magnetization).

[0039] The stand 2 is a base of the magnetizing device 1 and is equipped with at least a moving part 3 , a heating part 4 , a preheating part 5 , a magnetizing part 6 , a holding member 7 , a cooling part 8 , and a control part 10 .

[0040] Mobile unit 3 Figure 1The magnetized object 100 and the heating part 4 are relatively moved between the non-heating position and the heating position in the up-down direction, i.e., in the axial direction. The moving part 3 in the embodiment comprises a top plate 31, an actuator 32, and a heating part mounting base 33. The top plate 31 is arranged axially separated from the frame part 2, and the actuator 32 and the heating part mounting base 33 are fixed thereto. The actuator 32 enables the top plate 31 to move axially relative to the frame part 2. The actuator 32 is, for example, a direct-acting mechanism such as a hydraulic cylinder, which is powered by an external electric power not shown in the figure, and is driven and controlled by the control unit 10. A plurality of actuators 32 are arranged between the frame part 2 and the top plate 31, for example, two or four actuators are arranged. The heating part 4 is fixed to the heating part mounting base 33, and is fixed to the lower side of the top plate 31.

[0041] The heating section 4 performs magnetization heating on the magnetized object 100. The heating section 4 is made of a non-magnetic metal material, such as non-magnetic stainless steel, and heats the magnetized object 100 to a temperature above the Curie point of the magnet constituting the magnetized object 100. The heating section 4 in the embodiment is formed in a disk shape, and the upper side surface of the two surfaces in the upper and lower directions is fixed to the heating section mounting table 33 of the movable section 3, and the lower side surface is a heating surface (not shown). The heating surface is formed to have an outer diameter larger than the outer diameter of the magnetized object 100, and is axially opposite to the later-described mounting surface 6a of the excitation section 6. That is, the heating surface 4a is axially opposite to the magnetized object 100 mounted on the mounting surface (not shown) of the preheating section 5. In addition, the heating surface contacts the magnetized object 100 at the heating position. The heating section 4 has one or more heaters, which are powered by an external power not shown, and the temperature is controlled by the control section 10.

[0042] The preheating section 5 performs preliminary heating on the magnetized object 100. The preheating section 5 is made of non-magnetic metal material, and before reaching the heating position, heats the magnetized object 100 to a temperature lower than the Curie point (temperature higher than normal temperature) of the magnet constituting the magnetized object 100. Here, the preheating section 5 heats the magnetized object 100 placed on the magnetizing section 6 via the magnetizing section 6 and the retaining member 7. The preheating section 5 is powered by external power not shown in the figure, and has one or more heaters, and the temperature is controlled by the control section 10.

[0043] The excitation unit 6 generates a magnetic field to the magnetized object 100. The excitation unit 6 in the embodiment magnetizes the magnetized object 100 in the axial direction. After the magnetized object 100 is placed on the preheating unit 5, the excitation unit 6 is placed from the upper direction of the magnetized object 100, and then the magnetized object 100 and the excitation unit 6 are held and fixed on the preheating unit 5 through the retaining member 7 from the upper direction.

[0044] The field magnet used in the field magnet unit 6 is, for example, a rectangular samarium cobalt magnet (Sm-Co magnet, Curie temperature is usually 750° C. or higher and 900° C. or lower). Figure 2As shown, the permanent magnet 61 is a plurality of long strip-shaped N poles 62 and S poles 63 arranged alternately adjacent to each other. In the excitation unit 6, the N poles 62 and S poles 63 of the permanent magnet 61 are arranged in such a manner that the pole spacing in the magnetized object 100 after the magnetization process is less than 4 mm (but greater than 0 mm), preferably greater than 0.3 mm and less than 2.6 mm, and more preferably greater than 0.5 mm and less than 2.6 mm. Figure 3 1 is a schematic plan view for explaining the pole pitch in the magnetized object 100 , and shows a state in which the magnetized object 100 is magnetized with six poles alternately having N poles and S poles.

[0045] The cooling unit 8 cools the magnetized object 100 heated by the heating unit 4. The cooling unit 8 in the embodiment is fixed to the stand unit 2 by a fixing member not shown in the figure, and outputs air toward the magnetized object 100 placed on the excitation unit 6. The cooling unit 8 is, for example, an air-cooling fan, or a compressor that supplies compressed air, etc., and cools the heated magnetized object 100 by forced air cooling with high cooling efficiency rather than natural air cooling. The cooling unit 8 is powered by external power not shown in the figure, and the air supply is controlled by the control unit 10.

[0046] The control unit 10 controls the magnetization device 1 in order to magnetize the magnetized object 100. The control unit 10 controls the moving unit 3, the heating unit 4, the preheating unit 5 and the cooling unit 8. The control unit 10 drives and controls the moving unit 3 to move the heating unit 4 relative to the magnetized object 100 placed on the excitation unit 6 between the non-heating position and the heating position. Here, the so-called non-heating position is a position where the heating unit 4 is separated from the magnetized object 100 in the axial direction and is not in contact with the magnetized object 100, and is a position where the magnetized object 100 is not heated by the heating unit 4. On the other hand, the heating position is a position where the heating unit 4 is close to the magnetized object 100 in the axial direction and is in contact with the magnetized object 100, and the magnetized object 100 is heated by the heating unit 4.

[0047] The control unit 10 controls the temperature of the heating unit 4 so as to heat the heating unit 4 to a heating temperature above the Curie point of the magnet constituting the magnetized object 100. Specifically, in an embodiment, the heating unit 4 is heated to a temperature above the Curie point and below 350°C before reaching the heating position. The heating temperature is a temperature that can suppress the degradation of the magnetic properties of the magnet constituting the magnetized object 100. After heating the magnetized object 100 in a state of contact with the excitation unit 6, the cooling unit 8 cools the magnetized object 100 heated by the heating unit 4 to room temperature, thereby manufacturing the magnetized object 100.

[0048] Example

[0049] Hereinafter, the above-mentioned embodiment will be described in more detail based on examples. In addition, the above-mentioned embodiment is not limited at all by the following examples and comparative examples.

[0050] [Comparative Example 1, Example 2, Example 3]

[0051] As RTB-based sintered magnets, samples A to C were prepared corresponding to Comparative Example 1, Example 2, and Example 3. Samples A to C are all Nd-Fe-B-based sintered magnets manufactured by Shin-Etsu Chemical Co., Ltd. As shown in Table 1, Sample A is a trade name and model: N37, Sample B is a trade name and model: N39UH, and Sample C is a trade name and model: N32EZ.

[0052] [Table 1]

[0053] [Table 1]

[0054]

[0055] According to the chemical analysis results obtained by an electron probe analyzer (electron probe microanalyzer (EPMA)), each of samples A, B, and C contains dysprosium (Dy) as a heavy rare earth element, and the content thereof is in the relationship of sample A < sample B < sample C. Specifically, it is the analysis value shown in Table 1. In addition, the magnitude of the intrinsic coercive force of each sample A, B, and C is in the relationship of sample A < sample B < sample C. Therefore, sample C containing a large amount of dysprosium (Dy) as a heavy rare earth element becomes a sintered magnet with high heat resistance.

[0056] Next, use Figure 1 The magnetizing device 1 shown in the figure magnetizes each sample A, B, and C. Each sample A, B, and C is used as a magnetized object 100 and is made into a size of 7 mm × 7 mm × 1 mm thick. The excitation unit 6 as an excitation source for applying a magnetic field is composed of a plurality of substantially long permanent magnets (Sm2Co17 magnets) such as Figure 2 As shown in the figure, six N poles 62 and S poles 63 are arranged alternately at a predetermined pole pitch. Permanent magnets having pole pitches (magnetization pitches) of 0.32 mm, 0.67 mm, and 0.96 mm were prepared.

[0057] Each sample A, B, C is placed on the preheating part 5 of the magnetizing device 1 and is held by a graphite pressing plate (7mm×7mm×1mm thick) as a holding member 7. The excitation part 6 of the permanent magnet as the excitation source is in contact with the surface of each sample A, B, C. After heating to a temperature above the Curie temperature of each sample A, B, C and 350°C by the heating part 4 as the heating device, the sample is cooled to room temperature, thereby magnetizing the sample with a predetermined interpole pitch (0.32mm, 0.67mm, 0.96mm) in the thickness direction (axial direction) of the sample to obtain Figure 3 A magnetized object 100 is shown.

[0058] After cooling each sample A, B, and C to room temperature, a probe with a 50μm square Hall element was used, and the surface of each sample was kept at a distance of 0.14mm from the probe, and the magnetic field generated from the surface of each sample after magnetization was measured. In addition, as a comparative example, when pulse magnetization was performed on each sample A, B, and C, the magnetic field intensity at a position 0.14mm away from the surface of each sample was calculated. Regarding pulse magnetization, the magnetization device generally includes a magnetic wire and an electromagnetic soft iron, and is a mechanism that generates a magnetizing magnetic field by applying a pulse current to the wire. The wire diameter and the current value flowing are limited due to the risk of heat and wire breakage, and the current density is 16 [kA / mm 2 ] was calculated as the upper limit value.

[0059] [evaluate]

[0060] (Relationship between magnetic index and pole spacing)

[0061] Based on the relationship between the magnetic field generated from the surface of each sample A, B, and C after magnetization and the saturation residual magnetization, the magnetization index is calculated by the following formula (1).

[0062] Magnetization index = Maximum magnetic field generated from the sample surface after magnetization (mT) / saturation residual magnetization Jr (T) (1)

[0063] Figure 4 It’s about using Figure 1 The magnetization device 1 shown in the figure shows the relationship between the pole spacing (0.32mm, 0.67mm, 0.96mm) and the magnetization index of each sample after magnetizing each sample A, B, and C. In addition, Figure 5 This is a graph showing the relationship between the pole pitch (0.32mm, 0.67mm, 0.96mm) and the magnetization index for each sample A, B, and C after pulse magnetization as a comparative example. Figure 1The magnetization device 1 performed magnetization based on the cases of Comparative Example 1, Example 2, Example 3 and the case of pulse magnetization as a comparative example. The saturated residual magnetization, generated magnetic field and magnetization index of each sample A, B and C are shown in Tables 2 to 4.

[0064] [Table 2]

[0065] [Table 2]

[0066]

[0067]

[0068] [Table 3]

[0069] [Table 3]

[0070] Pole spacing (mm) 0.32 0.65 0.96 Generated magnetic field (mT): Example 2 147.0 306.2 379.5 Generated magnetic field (mT): Comparative example 145.8 351.2 457.3 Saturation residual magnetization (T): Example 2 1.19 1.19 1.19 Magnetic index ( / Jr): Example 2 123.6 257.5 319.1 Magnetic index ( / Jr): Comparative example 122.6 295.4 384.6

[0071] [Table 4]

[0072] [Table 4]

[0073] Pole spacing (mm) 0.32 0.65 0.96 Generated magnetic field (mT): Example 3 173.7 361.6 448.0 Generated magnetic field (mT): Comparative example 85.2 252.7 359.3 Saturation residual magnetization (T): Example 3 1.127 1.127 1.127 Magnetic index ( / Jr): Example 3 154.1 320.9 397.5 Magnetic index ( / Jr): Comparative example 75.6 224.2 318.8

[0074] As per Figure 5 As is also clear, when the pole pitch is reduced in the pulse magnetization based on the comparative example, the magnetization index of samples A to C decreases as the pole pitch decreases. In other words, as the pole pitch decreases, the magnetic field generated from the sample surface decreases. In addition, sample C (Example 3) with the largest inherent coercive force among the samples has a smaller magnetization index than the other samples.

[0075] On the other hand, Figure 4 As shown, it can be seen that Figure 1 In the magnetization process of the magnetization device 1 shown, the magnetization index of the sample C (Example 3) with the largest inherent coercive force among the samples is larger than that of the other samples. The reason is that when the pole spacing is reduced by the conventional pulse magnetization, if the inherent coercive force of the magnetized object 100 becomes larger, it is difficult to magnetize, and therefore the generated magnetic field after magnetization also becomes smaller. In contrast, when using Figure 1 When magnetizing is performed by the magnetizing device 1 shown, the magnetic field generated after magnetization can be increased even if the pole pitch is reduced, compared with the Nd-Fe-B system sintered magnet whose inherent coercive force is increased by adding a large amount of dysprosium (Dy) as a heavy rare earth element.

[0076] Figure 6 The graph shows the relationship between the interpolar spacing and the magnetization index in the sample C (Example 3) having the largest inherent coercive force among the samples. The value in the pulse magnetization based on the comparative example is the value obtained by calculation, Figure 1The values ​​of the magnetization performed by the magnetization device 1 shown are recorded when the pole pitch is greater than 1 mm. Figure 6 It can be seen that in the region less than 4 mm of the pole pitch, the magnetization by using the pulse magnetization method is better than that by using the pulse magnetization method by the comparative example. Figure 1 The magnetizing device 1 shown can improve the magnetizing index by magnetizing.

[0077] (Magnetic susceptibility ratio of each sample)

[0078] For each of the samples A, B, and C, the relationship between the magnetic field and the magnetization was determined, and the hysteresis curve was measured. Figure 7 : is a graph showing the first quadrant of the hysteresis curve for each sample A, B, and C. Figure 7 As is clear, the initial magnetization curves of Samples A and B rise sharply, but the initial magnetization curve of Sample C rises more gently than Samples A and B. In addition, it is known that when the magnetic field is greater than 200 kA / m, each sample has a gentle curve.

[0079] Next, as the magnetization ratio in each of Samples A, B, and C, the magnetization value (A) when an external magnetic field of 500 kA / m was applied in the initial magnetization curve relative to the saturation residual magnetization value (B) was calculated by the following formula (2).

[0080] Magnetization ratio (A / B) = magnetization in the initial magnetization curve (T) / saturation residual magnetization (T) (2)

[0081] In addition, Table 5 summarizes the values ​​of the magnetization ratio (A / B) of each sample A, B, and C.

[0082] In Table 5, the values ​​of magnetization (T) are the measured values ​​when a magnetic field of 3 T is applied (the values ​​from Figure 7 For Sample A and Sample B, the values ​​of saturation residual magnetization (T) are given from Figure 7 The value of saturation residual magnetization (T) in sample C was the value recorded in the report sheet of Shin-Etsu Chemical Co., Ltd., which is the manufacturer.

[0083] [Table 5]

[0084] [Table 5]

[0085] Comparative Example 1 (Sample A) Example 2 (Sample B) Example 3 (Sample C) A: Magnetization (T) 1.26 1.13 0.52 B: Saturation residual magnetization (T) 1.26 1.19 1.127 Magnetization ratio: A / B 1.0 0.95 0.46

[0086] In addition, the magnetization ratio was obtained for the case where an external magnetic field of 500 kA / m was applied in the initial magnetization curve. However, when the magnetic field was greater than 200 kA / m, each sample had a curve with a gentle rise in the initial magnetization curve. Therefore, 500 kA / m was used as a representative magnetization ratio near the saturation magnetization that was approximately horizontal. Therefore, the magnetization ratio can also be obtained in a magnetic field of about 400 kA / m to 700 kA / m.

[0087] The magnetization ratio is preferably less than 1.0. Furthermore, the magnetization ratio is more preferably less than 0.95, and more preferably less than 0.46. However, the magnetization ratio is greater than 0. If the magnetization ratio is less than 1.0, a magnet with high magnetization characteristics can be obtained relative to a high coercive force RTB system sintered magnet that is difficult to magnetize. In addition, if the magnetization ratio exceeds 1.0, a magnet with low magnetization characteristics becomes a magnet relative to a high coercive force RTB system sintered magnet that is difficult to magnetize, so it is not preferred.

[0088] Explanation of symbols

[0089] 1: Magnetic device

[0090] 2: Stand department

[0091] 3: Mobile Department

[0092] 4: Heating unit

[0093] 5: Preheating section

[0094] 6: Excitation department

[0095] 61: Permanent magnet

[0096] 62: N pole

[0097] 63: S pole

[0098] 7: Keep the component

[0099] 8: Cooling section

[0100] 10: Control Department

[0101] 32: Actuator

[0102] 33: Heating unit installation table

[0103] 100: Being attracted by a magnet

Claims

1. An RTB-based sintered magnet, which is an RTB-based sintered magnet (R represents a rare earth element including Nd, and T represents a transition metal element including Fe), wherein: The RTB based sintered magnet contains at least dysprosium (Dy) as a rare earth element. When the value of the saturation residual magnetization of the RTB system sintered magnet is B and the value of the magnetization when an external magnetic field of 500 kA / m in the initial magnetization curve is applied to the RTB system sintered magnet is A, the magnetization ratio is represented by A / B. In this case, the magnetization ratio is less than 1.0 (but greater than 0). The pole pitch in the RTB based sintered magnet is less than 4 mm (but greater than 0 mm).

2. The RTB based sintered magnet according to claim 1, wherein: The magnetization ratio is less than 0.

95.

3. The RTB based sintered magnet according to claim 1, wherein: The magnetization ratio is less than 0.

46.

4. A method for producing an RTB-based sintered magnet, which is a method for producing an RTB-based sintered magnet (R represents a rare earth element including Nd, and T represents a transition metal element including Fe), comprising: A step of preparing an RTB based sintered magnet, wherein the RTB based sintered magnet contains at least dysprosium (Dy) as a rare earth element, and when a value of saturation residual magnetization of the RTB based sintered magnet is set to B and a value of magnetization when an external magnetic field of 500 kA / m is applied to the RTB based sintered magnet in an initial magnetization curve is set to A, a magnetization ratio is represented by A / B, in which case the magnetization ratio is less than 1.0 (but greater than 0); and The RTB system sintered magnet is heated to a temperature above the Curie temperature of the RTB system sintered magnet and below the Curie temperature of the permanent magnet serving as the excitation source, and then cooled to room temperature. During this period, a magnetizing magnetic field is applied to the RTB system sintered magnet using the permanent magnet and magnetization is performed at a specified pole pitch.

5. The method for producing an RTB based sintered magnet according to claim 4, wherein: The magnetization ratio is less than 0.

95.

6. The method for producing an RTB based sintered magnet according to claim 4, wherein: The magnetization ratio is less than 0.

46.

7. The method for producing an RTB based sintered magnet according to any one of claims 4 to 6, wherein: The pole pitch in the RTB based sintered magnet is less than 4 mm (but greater than 0 mm).

8. The method for producing an RTB based sintered magnet according to claim 7, wherein: The heating to a temperature lower than the Curie temperature of the permanent magnet is heating to 350°C.

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