Manufacturing method for RTB sintered magnets

Abstract

To provide a manufacturing method of an R-T-B sintered magnet that enables wire electrical discharge machining to be performed more efficiently than a conventional method.SOLUTION: A manufacturing method of an R-T-B sintered magnet according to the present disclosure includes a magnet material preparation step of preparing an R-T-B sintered magnet material block, and a wire electrical discharge processing step of performing wire electrical discharge processing by wire extending in the vertical direction on the R-T-B sintered magnet material block to manufacture multiple R-T-B sintered magnets. In the wire electrical discharge processing step, a plurality of the R-T-B sintered magnet material blocks are arranged in a vertical direction and cut, and the dimension of the arranged R-T-B sintered magnet material blocks in the vertical direction is 9 mm or more and 65 mm or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present application relates to a method for producing an RTB based sintered magnet. [Background technology]

[0002] RTB sintered magnets (R is a rare earth element and must contain at least one selected from the group consisting of Nd, Pr, and Ce, T is Fe or Fe and Co, and B is boron) are classified into RFe 14 It consists of a main phase of a compound with a B-type crystal structure, a grain boundary phase located at the grain boundaries of this main phase, and a compound phase formed by the influence of trace additive elements and impurities. RTB-based sintered magnets have a high residual magnetic flux density B r (Hereafter, simply "B r ") and high coercive force H cJ (Hereafter, simply "H cJ ") and has excellent magnetic properties, making it known as the highest performance magnet among permanent magnets.

[0003] For this reason, RTB sintered magnets are used in a variety of motors in the automotive sector, including electric vehicles (EVs, HVs, PHVs), renewable energy sectors such as wind power generation, home appliances, and industrial sectors. RTB sintered magnets are an essential material for making these motors smaller, lighter, more efficient, and more energy-efficient (improving energy efficiency). RTB sintered magnets are also used in the drive motors of electric vehicles, and the replacement of internal combustion engine vehicles with electric vehicles contributes to preventing global warming by reducing greenhouse gases such as carbon dioxide (reducing fuel and exhaust gases). In this way, RTB sintered magnets are making a significant contribution to the realization of a green energy society.

[0004] An RTB sintered magnet is manufactured, for example, through the steps of preparing an alloy powder, press-molding the alloy powder to form a compact, and sintering the compact. The alloy powder is manufactured, for example, by the following method. First, an alloy is produced from a molten metal of various raw material metals by a method such as the ingot method or strip casting method. The obtained alloy is subjected to a pulverization process to obtain an alloy powder with a predetermined particle size distribution. This pulverization process usually includes a coarse pulverization process and a fine pulverization process, the former of which is carried out, for example, by utilizing the hydrogen embrittlement phenomenon, and the latter of which is carried out, for example, by using an airflow pulverizer (jet mill).

[0005] The sintered body obtained by the sintering process is then mechanically processed, such as by grinding and cutting, to produce individual pieces. Specifically, RTB rare earth magnet powder is first compressed in a press to produce a compact larger than the final magnet product. The compact is then sintered in a sintering process to produce a sintered body. If necessary, the sintered body may be subjected to a diffusion process in which a diffusion source containing rare earth element R is diffused from the surface to the interior of the magnet. The sintered or diffused sintered body is then ground, for example, with a cemented carbide blade saw or a rotating grinding wheel to give it the desired shape. For example, a block-shaped sintered body may first be produced, and then the sintered body may be sliced ​​with a blade saw or the like to produce multiple sintered bodies. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-303728 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, RTB sintered magnets are used in a wide variety of applications, and different shapes and sizes are required depending on user needs. One method for producing RTB sintered magnets of various shapes and sizes is to perform wire electrical discharge machining on an RTB sintered magnet material block to create the desired shape and size. However, when performing wire electrical discharge machining on an RTB sintered magnet material block, the slow machining speed makes it difficult to efficiently obtain the desired RTB sintered magnet. Therefore, an embodiment of the present disclosure provides a method for producing an RTB based sintered magnet that allows wire electrical discharge machining to be performed more efficiently than conventional methods. [Means for solving the problem]

[0008] In an exemplary embodiment, the method for producing an RTB based sintered magnet of the present disclosure includes a magnet material preparation step of preparing an RTB based sintered magnet material block (R is a rare earth element and must contain at least one selected from the group consisting of Nd, Pr, and Ce; T is Fe or Fe and Co; and B is boron); and a wire electrical discharge machining step of wire electrical discharge machining the RTB based sintered magnet material block using a wire extending in the vertical direction to produce a plurality of RTB based sintered magnets, wherein the wire electrical discharge machining step vertically arranges and cuts a plurality of the RTB based sintered magnet material blocks, and the dimension of the arranged RTB based sintered magnet material blocks in the vertical direction is 9 mm or more and 65 mm or less.

[0009] In one embodiment, the dimension of the RTB based sintered magnet material block in the vertical direction is 30 mm or more and 65 mm or less.

[0010] In one embodiment, in the wire electric discharge machining step, the plurality of sintered RTB magnet material blocks have gaps between them in the vertical direction, the gaps being between 0.5 mm and 50 mm.

[0011] In one embodiment, the gap is equal to or greater than 10 mm and equal to or less than 40 mm. [Effects of the Invention]

[0012] According to the embodiments of the present disclosure, it is possible to provide a method for producing an RTB based sintered magnet that allows wire electrical discharge machining to be performed more efficiently than conventional methods. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is an explanatory diagram that schematically illustrates an example configuration of a wire electric discharge machining apparatus that can be used in an embodiment of the present disclosure. [Figure 2] FIG. 2 is an explanatory diagram schematically illustrating an embodiment of the present disclosure in which the wire electric discharge machining apparatus of FIG. 1 is cutting an RTB based sintered magnet material block. [Figure 3] FIG. 3 is an explanatory diagram schematically showing a preferred embodiment of the present disclosure in which the wire electric discharge machining apparatus of FIG. 1 is cutting an RTB based sintered magnet material block. [Figure 4] FIG. 4 is an explanatory diagram showing the machining speed results of wire electric discharge machining in Experimental Example 1. [Figure 5] FIG. 5 is an explanatory diagram showing the machining speed results of wire electric discharge machining in Experimental Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present inventors have investigated cutting RTB-based sintered magnet material blocks using wire electrical discharge machining. They have found that when wire electrical discharge machining is performed on an RTB-based sintered magnet material block using a wire extending vertically, stacking multiple RTB-based sintered magnet material blocks of a specific thickness in the thickness direction (vertical direction) can increase the machining speed (the speed at which the wire passes through the RTB-based sintered magnet material block) compared to when wire electrical discharge machining is not performed on the RTB-based sintered magnet material block. The reason for this is unclear, but even when stacking the RTB-based sintered magnet material blocks results in no gaps (gaps of 0 mm or less), the machining fluid supplied to the RTB-based sintered magnet material block (described later) flows through the very small gaps in the overlapping areas, improving the discharge of machining sludge (processed RTB-based sintered magnet powder) from the RTB-based sintered magnet material block and improving the cooling of the wire, which is thought to result in the increased machining speed.

[0015] In this disclosure, a gap refers to a space between RTB based sintered magnet material blocks where no RTB based sintered magnet material blocks are present, and refers to a gap of more than 0 mm. Stacking without a gap is expressed as 0 mm or less. Even when stacking without a gap, it is difficult to achieve a completely zero gap due to the flatness of the RTB based sintered magnet material block surfaces in the stacked portion, and very small gaps are unavoidably formed, which is why the expression 0 mm or less is used.

[0016] Further investigation revealed that these effects can be significantly enhanced by setting the vertical dimension of the RTB based sintered magnet material block within a specific range.Further investigation revealed that when multiple RTB based sintered magnet material blocks are stacked in the vertical direction and processed, the processing speed can be further increased by providing a gap of a specific range between them in the vertical direction.

[0017] In this disclosure, the RTB based sintered magnet before wire electrical discharge machining is referred to as an RTB based sintered magnet material block, and the RTB based sintered magnet after wire electrical discharge machining is simply referred to as an RTB based sintered magnet.

[0018] Hereinafter, an embodiment of a method for producing an RTB rare earth sintered magnet according to the present disclosure will be described. (1) a magnet material preparation step of preparing an RTB sintered magnet material block; (2) a wire electrical discharge machining process in which a block of RTB sintered magnet material is subjected to wire electrical discharge machining using a wire extending vertically to produce a plurality of RTB sintered magnets; Includes.

[0019] Here, R is a rare earth element and must include at least one selected from the group consisting of Nd, Pr, and Ce, T is Fe or Fe and Co, and B is boron. Next, an example of a wire electric discharge machining apparatus that can be used in the embodiments of the present disclosure will be described.

[0020] FIG. 1 is an explanatory diagram schematically illustrating an example of the configuration of a wire electric discharge machining apparatus according to this embodiment. The illustrated wire electric discharge machining apparatus 100 includes a conductive stage 20 on which a workpiece (a block of RTB-based sintered magnet material) to be machined is placed, main guide wheels 40 and 42 that guide a wire 30 for electric discharge, and sub-guide wheels 44, 46, and 48 that guide the wire 30. Most of the wire 30 is wound around a drum 50. The wire 30 is made of, for example, molybdenum and has a length of, for example, 200 meters. The diameter of the wire 30 is, for example, approximately 0.2 mm. The running speed of the wire 30 (wire winding speed) during electric discharge machining is, for example, in the range of 40 m / min to 600 m / min. The tension of the wire 30 during running is, for example, in the range of 10 N to 15 N.

[0021] The stage 20 is driven by an actuator such as a motor. With a workpiece placed on it, the stage 20 can move at a predetermined speed in any direction within a plane parallel to the XY plane. More specifically, the stage 20 can move freely in any direction by combining movement in the X-axis direction and movement in the Y-axis direction. The movement speed of the stage 20 during wire electric discharge machining corresponds to the machining speed. Note that while the wire electric discharge machine described here uses the electric discharge wire repeatedly by rotating the drum 50 forward and backward, the wire electric discharge machine may also use the wire electric discharge only once by scanning it in only one direction. In this case, the wire electric discharge may be made of brass wire instead of molybdenum. Furthermore, because there are both small and large wire electric discharge machines, the running speed and tension of the wire 30 are not limited to the scope of this study.

[0022] FIG. 2 is a schematic diagram illustrating the state in which an RTB-based sintered magnet material block 10 is placed on a stage 20 and wire-cut electrical discharge machining is being performed. The RTB-based sintered magnet material block 10, which moves along with the stage 20, is being cut by a wire 30 extending vertically. During cutting, machining fluid is supplied to the RTB-based sintered magnet material block 10 from a machining fluid supply device (not shown). This supply method can be a known method similar to the method used to supply machining fluid to a magnet during normal grinding. Supplying machining fluid to the RTB-based sintered magnet material block has the effect of cooling the RTB-based sintered magnet material block during cutting and discharging machining sludge. The machining fluid is, for example, a water-soluble anti-rust lubricant. A pulsed high voltage is repeatedly applied between the stage 20 and the wire 30. As a result, an arc discharge occurs between the RTB-based sintered magnet material block 10 and the wire 30, scraping and cutting the surface of the RTB-based sintered magnet material block 10 facing the wire 30. Although the device for supplying machining fluid has been described, the present invention can also be applied to a wire electric discharge machining device in which the RTB sintered magnet material block 10 to be cut is submerged in a machining fluid tank for cutting.

[0023] The multiple RTB based sintered magnets produced by wire electrical discharge machining can include two or more RTB based sintered magnets that differ in at least one of size and shape. This makes it possible to quickly extract RTB based sintered magnets of the size and shape required by the user from multiple RTB based sintered magnet material blocks. This is suitable for high-mix, low-volume production. In the wire discharge process, the cutting direction by wire discharge includes a first direction (e.g., the X-axis direction) and a second direction (e.g., the Y-axis direction) perpendicular to the first direction, and the wire discharge is also performed during the operation of changing the cutting direction from the first direction to the second direction.

[0024] As shown in FIG. 2 , in this disclosure, multiple RTB based sintered magnet material blocks 10 are arranged vertically and then cut. The vertical direction in this disclosure refers to the Z-axis direction in FIG. 2 . A distinctive feature of this disclosure is that the vertical dimension of the RTB based sintered magnet material blocks arranged vertically is set to 9 mm or more and 65 mm or less. By setting the dimension within the 9 mm or more and 65 mm or less range, the processing speed can be improved compared to when multiple RTB based sintered magnet material blocks are not arranged vertically (when the RTB based sintered magnet material blocks are not stacked vertically). Note that 9 mm or more and 65 mm or less here refers to the dimension of a single RTB based sintered magnet material block. The vertical dimensions of the multiple arranged RTB based sintered magnet material blocks may differ from one another. To further improve the processing speed, the vertical dimension of the RTB based sintered magnet material block is preferably set to 30 mm or more and 65 mm or less. The RTB based sintered magnet material blocks may be stacked vertically by any method, for example, using a known fixing jig (such as a clamp).

[0025] More preferably, multiple RTB-based sintered magnet material blocks are arranged with a gap between them in the vertical direction and then cut. The gap is 0.5 mm or more and 50 mm or less. FIG. 3 is an explanatory diagram schematically showing a state in which wire electric discharge machining is performed on multiple RTB-based sintered magnet material blocks arranged with a gap between them in the vertical direction. As shown in FIG. 3, multiple RTB-based sintered magnet material blocks are arranged vertically with a gap 60 in the range of 0.5 mm or more and 50 mm or less, and wire electric discharge machining is performed using a wire 30 extending vertically. This promotes the discharge of machining fluid into the gap, further improving the machining speed. More preferably, the gap is 10 mm or more and 40 mm or less. This further improves the machining speed.

[0026] The dimensions of the RTB based sintered magnet material block are arbitrary. For example, when two rectangular parallelepiped RTB based sintered magnet material blocks measuring 100 mm x 100 mm x 50 mm are stacked vertically for wire electrical discharge machining, the vertical dimension of the RTB based sintered magnet material block should be 50 mm. The number of RTB based sintered magnet material blocks stacked vertically is also arbitrary. This can be determined appropriately depending on factors such as the size of the equipment. For example, two to five RTB based sintered magnet material blocks can be arranged vertically.

[0027] Hereinafter, an embodiment of the method for producing an RTB based sintered magnet according to the present invention will be described in detail. (1) A magnet material preparation process for preparing RTB sintered magnet material blocks <Alloy composition> In this embodiment, an alloy for an RTB-based sintered magnet is used. Here, R is a rare earth element and must contain at least one selected from the group consisting of Nd, Pr, and Ce. Examples of other rare earth elements include Ho and La. Preferred are Nd-Pr, Nd-Ce, Nd-La, Nd-Ce-La, Nd-Pr-Ce, Nd-Pr-La, Nd-Pr-Ce-La, Nd-Dy, Nd-Tb, Nd-Ho, Nd-Dy-Ho, Nd-Tb-Ho, Nd-Dy-Tb, Nd-Dy-Tb-Ho, Nd-Pr-Dy, Nd-Pr-Tb, Nd-Pr-Ho, Nd-Pr-Dy-Ho, Nd-Pr-Tb-Ho, Nd-Pr-Dy-Tb, and Nd-Pr-Dy-Tb-Ho. , Nd-Ce-Dy, Nd-Ce-Tb, Nd-Ce-Ho, Nd-Ce-Dy-Tb, Nd-Ce-Dy-Ho, Nd-Ce-Tb-Ho, Nd-Ce-Ho-Dy-Tb, Nd-Ce-Pr-Dy, Nd-Ce-Pr -Tb, Nd-Ce-Pr-Ho, Nd-Ce-Pr-Dy-Tb, Nd-Ce-Pr-Dy-Ho, Nd-Ce-Tb-Pr-Ho, Nd-Ce-Pr-Dy-Tb-Ho, Nd-La-Dy, Nd-La-Tb, Nd -La-Dy-Tb, Nd-La-Ho, Nd-La-Dy-Ho, Nd-La-Tb-Ho, Nd-La-Dy-Tb-Ho, Nd-La-Pr-Dy, Nd-La-Pr-Tb, Nd-La-Pr-Ho, Nd-La -Pr-Dy-Tb, Nd-La-Pr-Dy-Ho, Nd-La-Pr-Tb-Ho, Nd-La-Pr-Dy-Tb-Ho, Nd-Ce-La-Dy, Nd-Ce-La-Tb, Nd-Ce-La-Ho, Nd-Ce -La-Dy-Ho, Nd-Ce-La-Tb-Ho, Nd-Ce-La-Dy-Tb, Nd-Ce-La-Dy-Tb-Ho, Nd-Ce-Pr-La-Dy, Nd-Ce-Pr-La-Tb, Nd-Ce-Pr-La-Ho, Nd-Ce-Pr-La-Dy-Ho, Nd-Ce-Pr-La-Tb-Ho, Nd-Ce-Pr-La-Dy-Tb, Nd-Ce-Pr-La-Dy-Tb-Ho, etc.

[0028] Among R, Dy and Tb are particularly cJThe R content is, for example, 27% by mass or more and 35% by mass or less. Preferably, the R content of the alloy for an RTB based sintered magnet is 31% by mass or less (27% by mass or more and 31% by mass or less, preferably 28% by mass or more and 31% by mass or less). T is Fe or Fe and Co. For example, up to 50% of Fe may be substituted by cobalt (Co) by mass. Co is effective in improving temperature characteristics and corrosion resistance. The content of T may account for the remainder of R and B, or R, B, and M, which will be described later. The content of B may be a known content, and for example, a preferred range is 0.8 mass % to 1.2 mass %. If it is less than 0.8 mass %, high H cJ If it exceeds 1.2 mass%, B may not be obtained. r In addition, a part of B can be substituted with C (carbon).

[0029] In addition to the above elements, H cJ To improve the strength, an M element can be added. The M element is one or more selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, In, Sn, Hf, Ta, and W. The amount of M element added is preferably 5.0 mass% or less. If it exceeds 5.0 mass%, B r In addition, unavoidable impurities can be tolerated.

[0030] <Alloy preparation> Here is an example of a manufacturing process for an alloy for an RTB sintered magnet. An alloy ingot can be obtained by ingot casting, in which a metal or alloy previously prepared to have the composition described above is melted and poured into a mold. Alternatively, alloy flakes can be produced by a rapid cooling method, such as strip casting or centrifugal casting, in which the molten metal is brought into contact with a single roll, twin rolls, rotating disk, or rotating cylindrical mold, and quenched to produce a solidified alloy that is thinner than the alloy produced by the ingot method.

[0031] In the embodiments of the present disclosure, materials produced by either the ingot method or the quenching method can be used, but production by a quenching method such as strip casting is preferred. The thickness of the quenched alloy produced by the quenching method is usually in the range of 0.03 mm to 1 mm, and it is in the form of flakes. By subjecting the obtained alloy to hydrogen pulverization, the size of the hydrogen pulverized powder (coarsely pulverized powder) can be reduced to, for example, 1.0 mm or less. The coarsely pulverized powder obtained in this manner is pulverized in a jet mill.

[0032] <Alloy fine grinding process> The alloy powder for RTB sintered magnets is active and easily oxidized. For this reason, inert gases such as nitrogen, argon, and helium are used in jet mills to avoid the risk of heat generation and fire and to reduce the oxygen content as an impurity, thereby improving the performance of the magnet.

[0033] The material to be pulverized (coarsely pulverized powder) fed into the jet mill is pulverized into fine powder with a particle size distribution, for example, an average particle size (median diameter: d50) of 2.0 μm or more and 9 μm or less, and then collected by a cyclone collector. The cyclone collector is used to separate the powder from the airflow that carries it. Specifically, coarsely pulverized powder of alloy for RTB-based sintered magnets is pulverized in the upstream jet mill, and the fine powder generated by the pulverization is supplied to the cyclone collector together with the gas used for pulverization. A mixture of inert gas (pulverization gas) and the pulverized fine powder forms a high-velocity airflow and is sent to the cyclone collector. The cyclone collector is used to separate the pulverization gas from the fine powder. The fine powder separated from the pulverization gas is collected by a powder collector.

[0034] <Step of producing a molded body> Next, a compact is produced from the fine powder by pressing in a magnetic field. To prevent oxidation, the compact is preferably formed by pressing in an inert gas atmosphere or by wet pressing. The RTB-based sintered magnet material block may also be prepared without molding using a known method, such as the PLP (Press-Less Process) method described in JP-A-2006-19521.

[0035] The compact is then sintered to obtain an RTB-based sintered magnet material block. The sintering process for the RTB-based sintered magnet material block can be carried out, for example, in an inert gas atmosphere at a temperature ranging from 1000°C to 1150°C. To prevent oxidation during sintering, residual gas in the atmosphere can be replaced with an inert gas such as helium or argon.

[0036] (2) A wire electrical discharge machining process in which a block of RTB sintered magnet material is subjected to wire electrical discharge machining using a wire extending vertically to produce multiple RTB sintered magnets. The wire electric discharge machining process can be performed using, for example, the wire electric discharge machining apparatus 100 shown in FIG. 2 described above.

[0037] The cut RTB based sintered magnet may be subjected to known heat treatment, additional processing, surface treatment, etc. The method for producing an RTB based sintered magnet according to the present disclosure is not limited to the above embodiment. [Example]

[0038] Experimental Example 1 A number of RTB based sintered magnet material blocks were fabricated using a known method. The fabricated RTB based sintered magnet material blocks had a length of 60 mm, a width of 40 mm, and thicknesses (T) of 4.8 mm, 9.8 mm, 32.8 mm, and 62.3 mm.

[0039] Each of these RTB based sintered magnet material blocks was cut using the wire electric discharge machining device shown in Figure 2. Specifically, the RTB based sintered magnet material block was placed (set using a clamping jig) on ​​the stage 20 shown in Figure 2 with its thickness direction aligned vertically (vertical direction), and wire electric discharge machining was performed by moving the stage 20 in the length direction (60 mm). The electric discharge machining conditions may be, for example, a voltage of 10 to 20 V, a current of 2 to 10 A, with a pulse current turned on and off every tens to hundreds of microseconds, and the stage 20 scanned at a speed of 2 to 20 mm / min.

[0040] First, as a comparative example, wire-electrical discharge machining was performed on RTB-based sintered magnet material blocks with thicknesses of 32.8 mm and 62.8 mm, in which multiple RTB-based sintered magnet material blocks were not arranged vertically (only one RTB-based sintered magnet material block was used) (32.8 mm (integral) and 62.8 mm (integral) in Figure 4). Furthermore, as a comparative example, wire-electrical discharge machining was performed on an RTB-based sintered magnet material block with a thickness of 4.8 mm, which is outside the range of the present disclosure, even though two RTB-based sintered magnet material blocks were arranged vertically (4.8 mm two-stage in Figure 4). Next, as examples of the present invention, wire-electrical discharge machining was performed on RTB-based sintered magnet material blocks with thicknesses of 9.8 mm, 32.8 mm, and 62.3 mm, which are within the range of the present disclosure, arranged in pairs vertically (9.8 mm two-stage, 32.8 mm two-stage, and 62.3 mm two-stage in Figure 4). The RTB based sintered magnet material blocks stacked vertically do not have any gaps between them in the vertical direction (gaps of 0 mm or less, indicated as Gap 0 in the figure).

[0041] The results of the machining speed are shown in Figure 4. The machining speeds shown in Figure 4 are close to the maximum speed that can be achieved with the test equipment used (faster machining would likely damage or break the circuit board). As shown in Figure 4, the examples of the present invention (9.8 mm two-step, 32.8 mm two-step, and 62.3 mm two-step in Figure 4) all have higher machining speeds than the comparative examples (32.8 mm (integral), 62.8 mm (integral), and 4.8 mm two-step in Figure 4). In particular, the present invention examples with 32.8 mm two stages and 62.3 mm two stages have improved processing speeds compared to the comparative examples.

[0042] Experimental Example 2 A number of RTB based sintered magnet material blocks were produced in the same manner as in Experimental Example 1. The produced RTB based sintered magnet material blocks had a length of 60 mm, a width of 40 mm, and thicknesses (T) of 32.8 mm and 62.3 mm. These RTB based sintered magnet material blocks were subjected to wire electric discharge machining in the same manner as in Experimental Example 1.

[0043] First, as in Experimental Example 1, as a comparative example, wire electric discharge machining was performed on RTB based sintered magnet material blocks of 32.8 mm and 62.8 mm thickness, in which multiple RTB based sintered magnet material blocks were not arranged vertically (only one RTB based sintered magnet material block was used) (32.8 mm (integral) and 62.8 mm (integral) in Figure 5). Next, as an example of the present invention, two 32.8 mm thick RTB based sintered magnet material blocks were arranged vertically as shown in Figure 3. The two RTB based sintered magnet material blocks stacked vertically were positioned so that there was no gap between them in the vertical direction, and wire electric discharge machining was performed (gap of 0 mm or less, Gap 0 in Figure 5). Furthermore, as an example of the present invention, two 32.8 mm thick RTB based sintered magnet material blocks were arranged vertically as shown in Figure 3, with a gap of 0.5 mm to 60 mm between them in the vertical direction, and wire electric discharge machining was performed.

[0044] The results of the machining speed are shown in Figure 5. The machining speed shown in Figure 5 is close to the maximum speed that can be achieved with the test equipment used (if it is made any faster, there is a possibility of damage to the circuit board or breakage, etc.). As shown in Figure 5, the examples of the present invention having a gap (Gap 0.5 to 60 mm) have a higher machining speed than the comparative example (integral object). Furthermore, the examples of the present invention having a gap of 0.5 to 50 mm (Gap 0.5 to Gap 50 mm) have an even higher machining speed than the case where there is no gap (Gap 0). In particular, the examples of the present invention having a gap of 10 mm to 40 mm (Gap 10 mm to 40 mm) have an even higher machining speed. [Explanation of symbols]

[0045] 10. RTB-based sintered magnet material block 20 Stages 30. Discharge wire 40, 42... Main guide wheel 44, 46, 48... Sub guide wheels 50··· Winding drum

Claims

1. a magnetic material preparation step of preparing an R-T-B based sintered magnet material block (R is a rare earth element and must contain at least one element selected from the group consisting of Nd, Pr, and Ce, T is Fe or Fe and Co, and B is boron); a wire electric discharge machining process in which a block of sintered RTB based magnet material is subjected to wire electric discharge machining using a wire extending in the vertical direction to produce a plurality of sintered RTB based magnets; Including, The wire electric discharge machining step includes vertically arranging a plurality of the sintered RTB based magnet material blocks and cutting them; the dimension of the arranged RTB based sintered magnet material block in the vertical direction is 9 mm or more and 65 mm or less; A method for producing an RTB based sintered magnet.

2. 2. The method for producing a sintered RTB based magnet according to claim 1, wherein the dimension of the sintered RTB based magnet material block in the vertical direction is 30 mm or more and 65 mm or less.

3. 3. The method for producing a sintered R-T-B based magnet according to claim 1, wherein in the wire electric discharge machining step, the plurality of sintered R-T-B based magnet material blocks have gaps between them in the vertical direction, the gaps being 0.5 mm or more and 50 mm or less.

4. The method for producing a sintered RTB based magnet according to claim 3, wherein the gap is 10 mm or more and 40 mm or less.

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