CN107851506B

CN107851506B - Mold and method for forming permanent magnets from preforms and thermal deformation system

Info

Publication number: CN107851506B
Application number: CN201580080169.5A
Authority: CN
Inventors: 喻家庆; 陈必成
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-05-20
Filing date: 2015-05-20
Publication date: 2021-01-08
Anticipated expiration: 2035-05-20
Also published as: CN107851506A; WO2016183824A1; JP6463852B2; JP2018522400A

Abstract

The invention provides a mold (1, 101, 201, 301, 401) for forming a permanent magnet from a preform, the mold comprising a mold body (3,103,203,303,403), at least one mold cavity (5,105,205,305,405) formed in the mold body and having an input port (5,105,205,305,405) and an output port (7,107,207,307,407), wherein the at least one mold cavity comprises at least two parts, respectively, which open into each other, two adjacent parts of the at least two parts being angularly offset (α) with respect to each other. The invention also provides a hot deforming system including the mold and a method of forming permanent magnets from preforms using the hot deforming system. According to the present invention, grain growth can be suppressed, thereby allowing the final permanent magnet to have a high coercive force.

Description

Mold and method for forming permanent magnets from preforms and thermal deformation system

Technical Field

The present invention relates to manufacturing permanent magnets, and more particularly to a mold for forming permanent magnets from preforms, a method for forming permanent magnets from preforms, and a thermal deformation system including a mold for forming permanent magnets from preforms.

Background

Permanent magnets, such as rare earth/iron/boron-based permanent magnets, typically have sufficiently high remanence, coercivity and corrosion resistance, and are capable of providing sufficiently high magnetic flux over a wide temperature range, such as-40 ℃ to 180 ℃. Accordingly, permanent magnets such as rare earth/iron/boron-based permanent magnets are widely used in motors for Electric Vehicles (EV), Hybrid Electric Vehicles (HEV), household appliances, and the like. Motors with rare earth/iron/boron based permanent magnets have superior performance over induction motors due to reduced copper losses, high power density, high efficiency and low rotor inertia.

There are two known methods for making rare earth/iron/boron based permanent magnets. One is a metallurgical sintering process that generally includes strip casting, hydrogen decrepitation, jet milling, molding, sintering, and annealing. Permanent magnets made by a metallurgical sintering process are called sintered magnets, which are nearly full density and have a high magnetic energy product. Another is a bonding process that generally involves molding together the magnetic powder and organic binder (by compacting, injecting, pressing or calendering) and then curing at about 150 ℃. Permanent magnets made by the bonding process are referred to as bonded magnets, which are low density, normally contain more than 4% by volume of organic binder, and have a low magnetic energy product. Bonded magnets provide less magnetic flux than sintered magnets, but they can be molded into complex-shaped parts.

The uniaxial hot deformation process is a recent method for manufacturing rare earth/iron/boron-based permanent magnets. The method first cold presses a fine quenched magnetic ribbon or powder into a primary preform, then hot presses the primary preform into a magnetically isotropic magnet body, and finally performs a uniaxial heat deformation process on the magnetically isotropic magnet body. Under the applied pressure drive, the grains in the magnetically isotropic magnet body align their easy magnetization axes with the extrusion direction during uniaxial thermal deformation processing. As a result, the permanent magnet formed is magnetically anisotropic. Similar to the bonding process, the uniaxial hot deformation process is also a net shape process, and the magnet can be directly formed into a ring shape, a disk shape, a block shape, or other net shape.

In comparison with sintered magnets and bonded magnets, the hot deformed magnet produced by the uniaxial hot deformation process has a nanostructure in microstructure, magnetic properties with magnetic anisotropy, high magnetic energy product, high thermal stability due to small particle size, and requires only a small amount or even no heavy rare earth elements such as dysprosium and terbium to obtain high coercive force. These characteristics of the thermally deformable magnet are very attractive for electric vehicle/hybrid electric vehicle motors.

There are several processes to perform hot deformation processes such as upsetting, backward extrusion, forward extrusion, and rolling. These processes are carried out in specially designed molds at high temperatures (typically 650-. Hydraulic systems are used to generate mechanical pressure to squeeze the magnetic strip or powder into a designed chamber or through a designed track to densify the magnetic strip or powder and ultimately convert the magnetic strip or powder into a ring, disk, block or other shaped dense magnet. The magnetic strips or powders used may be pure magnetic strips/powders or may be a mixture of pure magnetic strips/powders with other pure magnetic strips/powders and non-magnetic strips/powders.

EP0513891B1 describes a process for hot pressing and/or hot working rare earth-containing powders using a press open to the air. The process first extrudes a rare earth-containing powder into a compact at room temperature using a solid lubricant only on the die wall, and then hot compresses the compact in a press open to the atmosphere using a heated die submerged in argon.

US7730755 describes a process of extruding a preform into a plate-shaped permanent magnet such that the cross-sectional dimension of the preform decreases in the X-direction and increases in the Y-direction perpendicular to the X-direction.

However, in these prior art hot deformation processes, when the compact or preform is pressurized or extruded at high temperature, particles in the compact or preform tend to grow, which deteriorates the coercive force of the final permanent magnet.

Therefore, there is a need for improvements to existing hot deformation processes.

Disclosure of Invention

The present invention provides a mold and method for forming a permanent magnet from a preform that can inhibit grain growth, thereby allowing the final permanent magnet to have a high coercivity.

According to an aspect of the present invention, there is provided a mold for forming a permanent magnet from a preform, comprising:

a mold body;

at least one die cavity formed in the die body and having an input port and an output port;

wherein the at least one mold cavity comprises at least two portions open to each other, respectively, two adjacent portions of the at least two portions being angularly offset with respect to each other.

Optionally, two adjacent portions of the at least two portions are configured such that the cross-sectional area of the latter portion is smaller than the cross-sectional area of the former portion.

Optionally, the angle is between 0 ° and 180 °, preferably between 45 ° and 135 °, more preferably 90 °.

Optionally, a curved transition is formed between two adjacent ones of the at least two portions.

Optionally, the at least two portions have a tapered or constant cross-section.

Optionally, the portion of the at least two portions defining the output port of the die cavity has a rectangular, circular, arcuate or triangular cross-section.

Optionally, the at least two portions are straight.

Optionally, the portion of the at least two portions defining the output port of the mold cavity is curved.

Optionally, the portion of the at least two portions defining the input port of the die cavity extends through the die body such that the die comprises two opposing input ports.

Optionally, the mould further comprises an additional port leading to and aligned with the part of the at least two parts immediately following the part of the mould cavity defining the input port.

According to another aspect of the present invention, there is provided a thermal deformation system comprising a mold for forming permanent magnets from a preform as described above.

Optionally, the hot deformation system further comprises a press comprising a ram that moves out of and into the mold cavity.

Optionally, the hot deformation system further comprises a feed mechanism for feeding the preform into the portion of the mold cavity defining the input port.

Optionally, the hot deformation system further comprises a heating mechanism for heating the preform to a predetermined temperature.

According to yet another aspect of the present invention, there is provided a method of forming a permanent magnet from a preform using the hot deformation system as described above, comprising the steps of:

feeding at least a portion of a preform through the input port into a first of the at least two portions of the mold cavity;

pressing the preform into the first of the at least two portions of the mold cavity at a predetermined temperature;

withdrawing the ram from the first portion of the mold cavity; and

the next preform is fed and pressed into the first portion to extrude the preform as a final permanent magnet from the output port of the die cavity.

Optionally, the steps are repeated to continuously perform a near net shape hot deformation on the plurality of preforms without interruption.

Optionally, the method further comprises the step of:

cutting the final permanent magnet into permanent magnet members.

These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be understood, however, that the drawings are designed solely for the purposes of illustration and description and not as a definition of the limits of the invention.

Drawings

Fig. 1A is a perspective view schematically showing a mold for forming a permanent magnet from a preform according to a first embodiment of the present invention;

FIG. 1B is a longitudinal cross-sectional view taken along line 1B-1B of FIG. 1A;

FIGS. 2A-2D schematically illustrate in longitudinal cross-section extrusion of a preform into a permanent magnet using a thermal deformation system including a mold according to a first embodiment of the present invention;

FIG. 2E schematically shows the resulting permanent magnet being extruded by the hot deformation system of FIGS. 2A-2D;

FIG. 3A schematically illustrates in longitudinal cross-section a thermal deformation system including a mold for forming permanent magnets from a preform according to a second embodiment of the present invention;

FIG. 3B is a longitudinal cross-sectional view taken along line 3B-3B of FIG. 3A;

FIG. 3C is a longitudinal cross-sectional view taken along line 3C-3C of FIG. 3A;

FIG. 3D schematically illustrates the resulting permanent magnet being extruded by the hot deformation system of FIGS. 3A-3C;

fig. 4A schematically shows, in a longitudinal cross-sectional view, a mold for forming a permanent magnet from a preform according to a third embodiment of the invention;

FIG. 4B is a longitudinal cross-sectional view taken along line 4B-4B of FIG. 4A;

FIG. 4C is a longitudinal cross-sectional view taken along line 4C-4C of FIG. 4A;

FIGS. 5A-5C schematically illustrate, in longitudinal cross-section, the extrusion of a preform into a permanent magnet using a thermal deformation system including a mold for forming a permanent magnet from the preform according to a fourth embodiment of the present invention;

fig. 6A schematically shows, in a longitudinal cross-sectional view, a mold for forming a permanent magnet from a preform according to a fifth embodiment of the invention;

FIG. 6B is a longitudinal cross-sectional view taken along line 6B-6B of FIG. 6A;

FIG. 6C is a longitudinal cross-sectional view taken along line 6C-6C of FIG. 6A;

FIG. 6D is a left side view of the mold shown in FIG. 6A;

FIG. 6E schematically illustrates a large permanent sector being cut into a plurality of small permanent sector members;

7A-7D schematically illustrate, in longitudinal cross-section, the extrusion of a preform into a permanent magnet using a thermal deformation system including a mold for forming a permanent magnet from a preform according to a sixth embodiment of the present invention;

FIG. 7E schematically illustrates the resulting permanent magnet being extruded by the hot deformation system of FIGS. 7A-7D;

FIGS. 8A, 8B and 8C schematically illustrate in longitudinal cross-section extrusion of a preform into a permanent magnet using a thermal deformation system including a mold for forming a permanent magnet from a preform according to a seventh embodiment of the present invention; and

fig. 8D schematically shows the resulting permanent magnet pressed by the hot deformation system of fig. 8A-8C.

Detailed Description

As is known, the continuous process for the almost net shaping of hot deformed rare earth/iron/boron based permanent magnets generally comprises two steps: preparing a dense preform by cold and/or hot pressing the magnetic strip or powder; and extruding the preform into a permanent magnet by hot deformation processing the preform at a high temperature. The magnetic strips or powder are formed by known processes. The raw materials from which the preform is formed and the process of preparing the preform from the magnetic strip or powder are also known in the art, and thus a detailed description thereof is omitted. The present invention focuses primarily on how to extrude a preform into a permanent magnet using a thermal deformation system that includes a mold for forming the permanent magnet from the preform.

Fig. 1A is a perspective view showing a mold for forming a permanent magnet from a preform according to a first embodiment of the present invention, and fig. 1B is a longitudinal sectional view taken along line 1B-1B of fig. 1A. As shown in fig. 1A and 1B, a mold 1 for forming a permanent magnet from a preform according to a first embodiment of the present invention includes a mold body 3 and a hollow mold cavity 5 formed in the mold body 3. The mould cavity 5 substantially comprises a first portion 5a and a second portion 5b leading to the first portion 5a and offset at an angle a with respect to the first portion 5 a. Thus, the mould cavity 5 has an input port 7 at the end of the first part 5a and an output port 9 at the end of the second part 5 b. Although in the embodiment shown in fig. 1A and 1B the second portion 5B is offset at an angle α of 90 ° with respect to the first portion 5a, it is understood that the second portion 5B may be offset at an angle α of between 0 ° and 180 ° and preferably between 45 ° and 135 ° with respect to the first portion 5 a. Further, while the first and

second portions

5a, 5b have a rectangular cross-section, it should be understood that the first and

second portions

5a, 5b may have a cross-section of any suitable shape, such as circular, semi-circular, elliptical, or triangular. In the embodiment shown in fig. 1A and 1B, both the first portion 5a and the second portion 5B are shown as having a constant cross-section. It is also possible that the first portion 5a and the second portion 5b have a decreasing cross section. It should be noted, however, that in any case the cross-sectional area of the second portion 5b is smaller than the cross-sectional area of the first portion 5 a.

Fig. 2A and 2B schematically show in longitudinal cross-section the extrusion of a preform into a permanent magnet using a hot deformation system comprising a mold according to a first embodiment of the invention. As shown in fig. 2A and 2B, the hot deformation system 11 generally includes a mold 1 according to the first embodiment of the present invention and a press (not all shown) having a ram 13 capable of moving up and down. Of course, the thermal deformation system 11 also includes a feeding mechanism (not shown) for feeding a portion of the preform through the input port 7 of the mold cavity 5 to the first portion 5a of the mold cavity 5.

As shown in fig. 2A, the feed mechanism feeds at least a portion of a preform P1 made by known processes through the input port 7 of the mold cavity 5 to the first portion 5a of the mold cavity 5. Subsequently, the ram 13 of the press moves downward to press the preform P1 into the first portion 5a, as shown in fig. 2B. As the ram 13 of the press moves downward, the preform P1 is pressed further into the first portion 5a or partially extruded from the first portion 5a of the mold cavity 5 into the second portion 5b of the mold cavity 5, as shown in fig. 2C. After the preform P1 is pressed into the first portion 5a, the ram 13 of the press may be released and moved upward to withdraw from the first portion 5a of the mold cavity 5 for the feeding mechanism to feed a portion of the next preform P2 into the first portion 5a, as shown in fig. 2D. The ram 13 of the press is moved downwards again in order to press the next preform P2 downwards, so that the preform P1 is completely extruded out of the outlet port 9 of the mold cavity 5 as a final permanent magnet M by means of the next preform P2, as shown in fig. 2E. The feeding-pressing-withdrawing-feeding process is automatically, continuously and repeatedly performed so as to continuously perform almost net-shape thermal deformation on the plurality of preforms without interruption. It should be noted that the process shown in fig. 2A and 2B is carried out at high temperatures (typically 650 c to 850 c) in a suitable (atmospheric vacuum, inert gas, etc.) atmosphere, as is known. The thermal deformation system 11 may further include a heating mechanism for heating the preform to a predetermined temperature. Furthermore, in order to smoothly extrude the preform from the first portion 5a of the mold cavity 5 into the second portion 5b of the mold cavity 5, a curved transition 6 is formed between the first portion 5a and the second portion 5 b.

According to the process shown in fig. 2A-2D, as the ram 13 of the press presses the preform P1 into the first portion 5a of the mold cavity 5, the preform P1 is hot pressed to full density and thermally deformed into a flat plate-like magnet, and then sequentially pressed into the second portion 5b of the mold cavity 5 by the next hot pressed and thermally deformed preform P2 to perform a second thermal deformation. After the second hot deformation, the final permanent magnet M is extruded from the mold cavity 5 by the next hot pressed and hot deformed preform P2. During the second hot deformation, the preform P1 remains flat and plate-like (and may change size depending on the geometry of the second portion 5b of the mold cavity 5), and the particles in the preform may be refined by the stress-shear effect, resulting in an improved coercivity of the final permanent magnet M. After this process, the preform becomes a flat plate-like permanent magnet M in which the particles are oriented to have anisotropic magnetic properties (i.e., high remanence) and the particles are refined to have improved coercive force (i.e., high thermal stability).

Fig. 3A schematically illustrates a thermal deformation system including a mold for forming permanent magnets from a preform according to a second embodiment of the present invention in a longitudinal cross-sectional view, fig. 3B is a longitudinal cross-sectional view taken along line 3B-3B of fig. 3A, and fig. 3C is a longitudinal cross-sectional view taken along line 3C-3C of fig. 3A. The thermal deformation system including a mold for forming permanent magnets from a preform according to the second embodiment of the present invention is generally similar to the thermal deformation system shown in fig. 2A-2D. In a thermal deformation system including a mold according to a second embodiment of the present invention, the same or similar components as those in the thermal deformation system shown in fig. 2A to 2D are denoted by the same reference numerals plus "100". The description of the same or similar components is omitted for the sake of simplicity and brevity. The thermal deformation system 111 comprising the mold 101 according to the second embodiment of the present invention differs from the thermal deformation system 11 shown in fig. 2A-2D in that: the second portion 105b of the mold cavity 105 has an arcuate cross-section rather than a rectangular cross-section. The resulting permanent magnet M, which is extruded out of the output port 109 of the die cavity 105, is thus an arc-shaped plate as shown in fig. 3D.

Although the resulting permanent magnet M according to the present invention is shown as being flat plate-like (as shown in fig. 2E) or arc-like (as shown in fig. 3D), the resulting permanent magnet M may be of any suitable shape by selecting the shape of the cross-section of the portion of the die cavity defining the output port. For example, by designing the shape of the cross-section of the part of the mould cavity defining the output port to have a circular or triangular cross-section, the resulting permanent magnet M according to the invention may be a rod having a circular or triangular cross-section. The resulting permanent magnet M according to the invention may be further cut into a plurality of shorter or smaller disk, block, fan or other shaped magnet members and may be used directly in a motor after being polished. By varying the cross-sectional dimensions of the portion of the die cavity defining the output port, the dimensions of these small magnet members can be adjusted accordingly.

Fig. 4A schematically shows a mold for forming a permanent magnet from a preform according to a third embodiment of the invention in a longitudinal sectional view, fig. 4B is a longitudinal sectional view taken along line 4B-4B of fig. 4A, and fig. 4C is a longitudinal sectional view taken along line 4C-4C of fig. 4A. A mold for forming a permanent magnet from a preform according to a third embodiment of the present invention is substantially similar to the mold shown in fig. 1A and 1B. In the mold according to the third embodiment of the present invention, the same or similar parts as those of the mold shown in fig. 1A and 1B are denoted by the same reference numerals plus "200". The description of the same or similar components is omitted for the sake of simplicity and brevity. The mold 201 according to the third embodiment of the present invention differs from the mold 1 shown in fig. 2A-2D in that the mold cavity 205 comprises four sections, namely a first section 205a, a second section 205b, a third section 205c and a fourth section 205D. Similarly, each of the four portions of the mold cavity 205 is offset at an angle α relative to the adjacent portions. Also, the latter of the four portions of the mold cavity 205 has a smaller cross-sectional area than the former. Although in the illustrated embodiment the mold cavity is shown as having two or four sections, the mold cavity may have three or more than four sections. The more portions of the mold cavity, the more thermal deformation the preform undergoes. As a result, the final permanent magnet M has a further refined particle size in the microstructure (such as a further refined nano-structured particle size) to achieve a high coercivity but still maintain a high magnetocrystalline anisotropy.

Fig. 5A-5C schematically illustrate, in longitudinal cross-section, the extrusion of a preform into a permanent magnet using a thermal deformation system including a mold for forming a permanent magnet from a preform according to a fourth embodiment of the present invention. The thermal deformation system including a mold for forming permanent magnets from a preform according to the fourth embodiment of the present invention is generally similar to the thermal deformation system shown in fig. 2A-2D. In a thermal deformation system including a mold according to a fourth embodiment of the present invention, the same or similar components as those in the thermal deformation system shown in fig. 2A-2D are denoted by the same reference numerals plus "300". The description of the same or similar components is omitted for the sake of simplicity and brevity. The thermal deformation system 311 including the mold 301 according to the fourth embodiment of the present invention is different from the thermal deformation system 11 shown in fig. 2A to 2D in that: the die 301 includes two die cavities 305 formed in the die body 301. Each mold cavity 305 includes a first portion 305a and a second portion 305b that is offset at an angle a relative to the first portion 305 a. It should be understood that a mold comprising more than two mold cavities is also possible. The mold including more than one mold cavity can simultaneously manufacture more than one magnet through a thermal deformation process, thereby improving production efficiency.

Fig. 6A schematically shows a mold for forming a permanent magnet from a preform according to a fifth embodiment of the invention in a longitudinal sectional view, fig. 6B is a longitudinal sectional view taken along line 6B-6B of fig. 6A, fig. 6C is a longitudinal sectional view taken along line 6C-6C of fig. 6A, and fig. 6D is a left side view of the mold shown in fig. 6A. A mold for forming a permanent magnet from a preform according to a fifth embodiment of the present invention is substantially similar to the mold shown in fig. 1A and 1B. In the mold according to the fifth embodiment of the present invention, the same or similar parts as those of the mold shown in fig. 1A and 1B are denoted by the same reference numerals plus "400". The description of the same or similar components is omitted for the sake of simplicity and brevity. The mold 401 according to the fifth embodiment of the present invention differs from the mold 1 shown in fig. 1A and 1B in that the second portion 405B of the mold cavity 405 is curved instead of straight. Second portion 405b of mold cavity 405 may be designed to have a gradually decreasing cross-section to form a fan-shaped permanent magnet. The fan-shaped permanent magnets may be cut into a plurality of small fan-shaped magnet members (as shown in fig. 6E), which may be used after polishing. During the thermal deformation process, the particles in the microstructure are oriented in a direction perpendicular to the thickness direction of the magnet.

In the preferred embodiment, while only the upper ram is used to press the preform into the mold cavity, it is possible to use more than one ram at a time. Fig. 7A-7D schematically illustrate, in longitudinal cross-section, the extrusion of a preform into a permanent magnet using a thermal deformation system including a mold for forming a permanent magnet from a preform according to a sixth embodiment of the present invention. A thermal deformation system including a mold for forming permanent magnets from a preform according to a sixth embodiment of the present invention is substantially similar to the thermal deformation system shown in fig. 2A-2D. In a thermal deformation system including a mold according to a sixth embodiment of the present invention, the same or similar components as those in the thermal deformation system shown in fig. 2A to 2D are denoted by the same reference numerals plus "500". The description of the same or similar components is omitted for the sake of simplicity and brevity. The thermal deformation system 511 comprising the mold 501 according to the sixth embodiment of the present invention differs from the thermal deformation system 11 shown in fig. 2A-2D in that: a first portion 505a of the mold cavity 505 extends through the mold body 501 such that the first portion 505a defines a first input port 507a and a second input port 507 b. As a result, the press includes an upper ram 513a and a lower ram 513 b. In use, two preforms P1 may be fed into the first portion 505a of the mold cavity 505 through the first input port 507a and the second input port 507b of the mold cavity 505. Fig. 7E schematically shows the resulting permanent magnet pressed by the hot deformation system of fig. 7A-7D. In order to smoothly extrude the preform from the first portion 505a into the second portion 505b of the mold cavity 505, the ends of the upper ram 513a and the lower ram 513b define respective

curved portions

514a, 514b that contact the preform when it is being compressed.

Fig. 8A, 8B and 8C schematically illustrate in longitudinal cross-section the extrusion of a preform into a permanent magnet using a thermal deformation system including a mold for forming a permanent magnet from a preform according to a seventh embodiment of the present invention. A thermal deformation system 611 including a mold 601 according to a seventh embodiment of the present invention is different from the thermal deformation system 601 shown in fig. 7A to 7D in that: the mold 601 also includes an additional port 608 that opens into the first portion 605a of the mold cavity 505 and aligns with the second portion 605 b. As a result, the press includes an additional ram 613c in addition to the upper ram 613a and the lower ram 613 b. Thus, the additional ram 613c helps to smoothly extrude the preform from the first portion 605a into the second portion 605b of the mold cavity 605.

When the press includes at least an upper ram and a lower ram as shown in fig. 7A-7D and 8A-8C, the preform may be pressed in two opposite directions simultaneously. As a result, the microstructure of the final permanent magnet is more homogenous and the mechanical and magnetic properties of the final permanent magnet are also more uniform.

In the above-described embodiments, by designing the mold cavity of the mold for forming the permanent magnet from the preform to have at least two portions that are offset with respect to each other, the preform undergoes at least two hot press deformations as the preform is pressed through the mold in order to further reduce the particle size. As a result, the final permanent magnet has a high coercive force.

The mold and process according to the invention can be used to manufacture permanent magnets that are rich in rare earths and contain less rare earths in terms of chemical composition. The resulting permanent magnet can be a single phase nanostructured or nanocomposite material, respectively.

It should be noted that embodiments of the present invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method claims, whereas other embodiments are described with reference to apparatus claims. However, a person skilled in the art will gather from the above and the following description that, unless other notified, in addition to any combination of features belonging to one type of subject-matter also any combination between features relating to different subject-matters is considered to be disclosed with this application. However, all features may be combined, as long as the synergistic effect is greater than a simple superposition of the features.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several means recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Reference signs in the claims shall not be construed as limiting the scope.

Claims

1. A mold (1, 101, 201, 301, 401) for forming permanent magnets (M) from preforms, comprising:

a die body (3,103,203,303,403);

at least one die cavity (5,105,205,305,405) formed in the die body (3,103,203,303,403) and having an input port (7,107,207,307,407) and an output port (9,109,209,309,409);

wherein the at least one mould cavity comprises at least two portions opening into each other, respectively, two adjacent portions of the at least two portions being angularly offset (a) with respect to each other;

wherein the portion of the at least two portions defining the input port of the mold cavity extends through the mold body such that the mold includes two opposing input ports; and

the mold further includes an additional port opening into and aligned with a portion of the at least two portions that defines the input port immediately following the portion of the at least two portions.

2. The mold (1, 101, 201, 301, 401) according to claim 1, wherein two adjacent portions of said at least two portions are configured such that the cross-sectional area of a subsequent portion is smaller than the cross-sectional area of a preceding portion.

3. The mold (1, 101, 201, 301, 401) according to claim 1, wherein said angle (a) is between 0 ° and 180 °.

4. The mold (1, 101, 201, 301, 401) according to claim 1, wherein a curved transition is formed between two adjacent portions of said at least two portions.

5. The mold (1, 101, 201, 301, 401) according to claim 1, wherein said at least two portions have a tapered or constant cross section.

6. The die (1, 101, 201, 301, 401) of claim 1, wherein a portion of the at least two portions defining the output port of the die cavity has a rectangular, circular, arcuate, or triangular cross-section.

7. The mold (1, 101, 201, 301, 401) of claim 1, wherein said at least two portions are straight.

8. The mold (1, 101, 201, 301, 401) of claim 1, wherein a portion of said at least two portions defining an output port of said mold cavity is curved.

9. The mold (1, 101, 201, 301, 401) according to claim 1, wherein said angle (a) is between 45 ° and 135 °.

10. The mold (1, 101, 201, 301, 401) according to claim 1, wherein said angle (α) is 90 °.

11. A hot deformation system comprising a mold (1, 101, 201, 301, 401) for forming permanent magnets (M) from preforms according to any one of claims 1 to 10.

12. The thermal deformation system of claim 11, further comprising:

a press including a ram that moves out of and into the mold cavity.

13. The thermal deformation system of claim 12, further comprising:

a feed mechanism for feeding the preform into the portion of the mold cavity defining the input port.

14. The thermal deformation system of claim 12, further comprising:

a heating mechanism for heating the preform to a predetermined temperature.

15. A method of forming a permanent magnet from a preform using the hot deformation system of any of claims 11-14, comprising the steps of:

withdrawing a ram from the first portion of the mold cavity; and

16. The method of claim 15, wherein the steps are repeated to continuously perform near net shape thermal deformation on the plurality of preforms without interruption.

17. The method of claim 15 or 16, further comprising the step of:

cutting the final permanent magnet into permanent magnet members.