Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
  • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
  • H01F1/047—Alloys characterised by their composition
  • H01F1/053—Alloys characterised by their composition containing rare earth metals
  • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
  • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
  • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
  • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
  • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered

Definitions

• the invention relates to a sintered permanent magnet or material consisting essentially of a magnetic phase of the type SE2 (FeCo) 14B and at least one further sinter-active or grain-connecting phase which contains heavy rare earths and / or compounds. Furthermore, the invention relates to a method for producing rare earth-containing permanent magnet (s) (- materials), wherein at least the magnetic phase of the type SE2 (FeCo) 14B forming or containing constituent is produced by melt metallurgy and then pulverized, whereupon the powder is pressed with additives containing heavy rare earths in the magnetic field and then sintered to form a magnetizable raw body and optionally heat-treated.
• s rare earth-containing permanent magnet
• Permanent magnets or permanent magnet materials made essentially of an alloy of iron (Fe), boron (B) and rare earths (SE) in the sintering process are preferably used when high coercive force, high remanence and / or large energy product are required.
• the constituent which forms or contains the magnetic phase of the Se2Fe14B type is produced by melt metallurgy and pulverized, which powder, if appropriate mixed with additives, is pressed into a green compact in the magnetic field and this is sintered, the sintered body optionally being subjected to at least one further heat treatment.
• EP-B1-0126802 discloses sintered permanent magnets of the Fe-BR type (R means at least one SE element including Y), in which Fe can be partially replaced by Co.
• the elements are homogeneously distributed in the magnetic phase due to the manufacturing process used, and a heat or aging treatment of the sintered body is said to improve the magnetic values. If Fe is partially replaced by Co, this increases the Curie point or the Curie temperature (T c ) of the magnetic material, but its coercive force, as is known to the person skilled in the art, however decreases with increasing Co content, whereby the energy product can also be adversely affected.
• the invention has for its object to eliminate the disadvantages of the known SE-containing magnets (materials) and their manufacturing processes and to create sintered permanent magnets that have high saturation magnetization, high coercive force and large energy product with good temperature stability and high Curie point. It is also the object of the invention to provide a new and improved manufacturing method for magnets, with which high magnetic characteristics can be achieved and their scatter can be reduced.
• grains of the magnetic phase are surface-smoothed or diffusion molded and have a diameter of at most 60 ⁇ m, but at least 3 ⁇ m. Grain surfaces designed in this way are energetically dependent, at least make it difficult to form and / or shift the domain walls, which generally improves the coercive force values.
• a corresponding grain size of the magnetic phase is of great importance because, as has been found, grain diameters of greater than 60 ⁇ m and less than 3 ⁇ m lead to a decrease in the coercive force or the magnetic induction to lead.
• a special feature of the new permanent magnet (material) according to the invention is a partial replacement of iron (Fe) by cobalt (Co) in the magnetic phase formed with boron (B) and light rare earths (LSE) and heavy rare earths (SSE) , where the average SSE content is set at a certain value depending on the concentration value of Co. It is known that Co contents cause a slight increase in magnetization and an increase in the Curie point, but the coercive force or magnetic induction is reduced, which leads to a lower energy product (BH max ) of the magnet and thus to a deterioration in all of the magnetic properties.
• BH max lower energy product
• LSE magnetic moments of LSE, in particular the advantageously usable elements neodymium (Nd) and praseodymium (Pr), are aligned parallel to Fe or ferromagnetic and the SSE has an antiparallel direction to Fe or an antiferromagnetic direction of its have magnetic moments.
• SSE Dyprosium (Dy) has been shown to be particularly effective and advantageous because, among other things, the anisotropy field strength increases sharply due to the antiferromagnetic coupling.
• the SSE content be at least 0.05 times the weight of Co, because lower concentrations cause a reduction in the coercive force.
• SSE contents higher than 0.2 times the weight of Co lead to a decrease in the saturation magnetization.
• the local concentration of SSE atoms is inhomogeneous across the diameter of the grains, in particular increasing towards the surface-smoothed grain boundary, domain wall formation and / or domain wall displacement is further reduced, as a result of which the coercive force and the result of the energy product are further increased .
• An at least 3 times higher concentration of SSE atoms in a range of at most 1 ⁇ m at the grain boundary has proven to be particularly effective.
• Another particularly important characteristic of the new permanent magnet according to the invention is a higher SSE content than the hard magnetic phase and / or a higher SSE activity at the diffusion temperature of the sinter-active or grain-connecting, essentially paramagnetic phase.
• Good magnetic values are preferably obtained if the SE concentrations of this grain-connecting phase are at least 25% and their SSE concentrations are at least 90% greater than those of the magnetic phase on average.
• the constituent which forms or contains the hard magnetic phase of the type SE2 (FeCo) 14B is produced by melting and casting an alloy containing in AT% 8 to 30 rare earths (SE), 2 to 28 B, remainder Fe and Co, if necessary, further alloying elements and impurities in which Co is adjusted with a concentration of 3 to 25 at.%, preferably 6 to 20 at.%, in particular 8 to 14 at.%, and the RE content consists of light rare earths ( LSE) and heavy rare earths (SSE) are formed, manufactured and ground into powders with a grain size of at least 3 ⁇ m, but, as is known per se, less than 60 ⁇ m, preferably less than 45 ⁇ m, in particular less than 30 ⁇ m.
• SE rare earths
• SSE heavy rare earths
• This powder contains one or more additive (s) containing rare earths (SE) with an SE concentration which is at least 25%, preferably at least 35%, in particular at least 80% greater than the powder grains and one at least 100%, preferably 150%, in particular 200%, greater SSE concentration introduced and distributed homogeneously.
• SE rare earths
• the additives can also be introduced into the powder in liquid form, for example as SE compounds.
• the SS content as a function of the Co content is adjusted in a range from 0.02 to 0.19 times the Co content by the melt metallurgical route.
• the SSE content of the additive is intended to be at least 100% greater than that of the powder.
• a green compact is pressed from the material formed from powder with the additives, which is preferably sintered in a vacuum or, if appropriate, in a protective gas atmosphere at high temperature.
• the additives become at least partially liquid or pasty, essentially envelop the grains and act as a sinter-active or grain-binding agent which largely fills the edges and fissures in and between the grains.
• the sintering temperature is selected for a short time to such an extent that the sintering agent is given a sufficient degree of liquid to in particular fill or envelop the fissures and sharp-edged concave cavities of the grain surfaces.
• the sintered body is subjected to a diffusion treatment or diffusion annealing at a temperature below the sintering temperature at a temperature between 600 and 100 ° C. and for a period of 1 to 12 hours.
• the sinter-active or grain-connecting phase or mass has a sufficient degree of strength for shape stabilization.
• a Diffusion treatment of the sintered body which can be connected directly to the sintering, achieves surface structures and concentration profiles of atoms which are advantageous for the grains for the magnetic properties.
• the surfaces of the grains forming or containing the hard magnetic phase which are made sharp-edged by the comminution process, are smoothed because the edges or tips represent energy irregularities and an increased atom diffusion takes place in these areas.
• a shaping of the grains or a largely directed atom diffusion brings about a reduction or minimization of their surface energy. Due to smoothed surfaces with reduced energy of the grains from the hard magnetic phase, based on the change in direction of the magnetic moments, a new formation of domain walls, which preferably occurs at the tips and edges, is effectively reduced and thus the coercive force of the magnets is increased.
• a certain grain size specified above and a sufficient filling, in particular the fissures and sharp-edged concave cavities of the grain surfaces with sinter-active mass or phase are important.
• SSE atoms Due to the set concentration difference of SSE atoms in the hard magnetic phase and the grain-connecting, largely paramagnetic phase, SSE atoms also penetrate into the magnetocrystalline phase during the diffusion treatment. Because in the case of elements diffused in, such as AL, for example, a rapid, essentially immediate, concentration equalization takes place, it was surprising that SSE atoms at the grain boundaries or in the region near the grain boundaries can be enriched to at least 3 times the content compared to the grain interior and one inhomogeneous concentration of SSE atoms can be formed in the grains. It is important to choose the diffusion treatment parameters in such a way that the strength of the area of the increased SSE concentration is set to at least 0.05 ⁇ m, but at most 1 ⁇ m. Smaller strengths only cause an insignificant further reduction in the formation of the domain wall and / or domain wall mobility, thus a slight increase in coercive force; greater strengths reduce the achievable saturation magnetization and reduce the energy product of the permanent magnet.
• Table 1 shows the magnetic values of reference magnets (materials) with different compositions.
• the respective starting material was produced by melt metallurgy and ground into powder. Under the influence of a magnetic field, the powder was pressed into a green body, which was sintered, heat-treated and magnetized.
• the composition and the measured magnetic values of the permanent magnet bodies are given under the designations A to F in Table 1.
• the permanent magnets (materials) according to the invention are listed under numbers 1 to 14 in Table 2.
• the analytical determinations were carried out by transmission electron microscopy (TEM).
• TEM transmission electron microscopy
• the SSE content in the magnetic phase on average was determined by averaging from point and area measurements over the grain cross section.
• the Co content and the magnetic field strength or the magnetization are increased by the Co content and, as has been shown, the coercive force or induction is kept at high values as a result of the further measures, which synergistically brings about an increased energy product .
• conventional magnets largely without Co content, high coercive forces become low at low Curie temperatures and at high Co content high magnetization achieved at high Curie temperatures.
• the magnetic energy product is relatively low in both cases.

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• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Hard Magnetic Materials (AREA)
• Powder Metallurgy (AREA)
• Manufacturing Cores, Coils, And Magnets (AREA)
• Compounds Of Iron (AREA)

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• 1991
  • 1991-02-11 AT AT0028791A patent/AT398861B/de not_active IP Right Cessation
• 1992
  • 1992-02-10 DE DE59200795T patent/DE59200795D1/de not_active Expired - Fee Related
  • 1992-02-10 AT AT92890030T patent/ATE114383T1/de not_active IP Right Cessation
  • 1992-02-10 PL PL92293427A patent/PL169844B1/pl unknown
  • 1992-02-10 HU HU9200403A patent/HU213284B/hu not_active IP Right Cessation
  • 1992-02-10 EP EP92890030A patent/EP0499600B1/de not_active Expired - Lifetime
  • 1992-02-10 CZ CS92392A patent/CZ281161B6/cs unknown

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