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
  • H01F1/0578—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 bonded together
• • 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
  • H01F1/0572—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 with a protective layer
• • 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
  • H01F1/0576—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 pressed, e.g. hot working

Definitions

• Permanent magnet materials are a basic material for many electrical and electronic applications such as motors, microphones, loudspeakers, measuring devices etc. or for daily needs, e.g. as simple holding magnets.
• ferrites, alnico magnets or rare earth cobalt magnets are mainly used for these purposes.
• the low magnetic performance is a disadvantage of the first two types, it is the low availability of the SE raw material samarium and the high price of the connection for the SE cobalt magnets.
• Great efforts have therefore been made to find a new alloy that is characterized on the one hand by good magnetic properties such as high coercive force and high remanence, and on the other hand by cheaper raw materials that are available in larger quantities.
• the SE-Fe-B alloy is produced by melt metallurgy under vacuum or inert gas in order to prevent oxygen uptake by the rare earth metals, which tend to oxidize.
• the alloy is produced in pieces or in the form of ingots. To improve the magnetic properties, it must be crushed.
• the comminution of the alloy takes place either by atomization into powder (US Pat. No. 4,585,473) or in the so-called "melt spinning" process (US Pat. No. 4,496,395), whereby amorphous structures are formed, by a pressure roller or by Bre and grinding the alloy. In this way, the alloy particles are brought to grain sizes between 1 and 10 microns. With this fineness, they are extremely sensitive to oxidation.
• the absorption of oxygen primarily binds the rare earth metal, eg neodymium, in the form of an oxide and is therefore no longer available for the Nd-Fe-B phase, which is responsible for achieving the hard magnetic properties. From a certain oxygen concentration, this leads to a significant loss of quality and, at higher values, even to a complete loss of magnetic properties.
• the powders must therefore be protected against atmospheric oxygen, processed further under an inert gas atmosphere or in organic solvents. This is usually done by pressing, possibly with the application of an external magnetic field, whereby anisotropic or isotropic magnets are obtained.
• the compacts are then sintered and the sinterings are subjected to a thermal aftertreatment to improve the magnetic properties. It is only through the process of sintering that the magnet regains extensive resistance to oxidation. Complete resistance of the magnet can only be achieved by coating it.
• the magnets produced according to these described processes must therefore be subjected to a sintering treatment under vacuum or an inert gas atmosphere, which must run at over 1000 ° C and only leads to high-quality products in connection with a subsequent heat treatment. This represents a costly process step.
• the powders produced according to the "melt spinning" process with subsequent comminution are usually embedded in plastic, resulting in isotropic magnets with a low energy product (BHmax).
• the aim of the present invention is therefore a process for the production of corrosion-resistant, hard magnetic powders from an alloy of the basic type SE-Fe-B for magnet production, the magnetic powders produced in this way being distinguished by excellent resistance to oxidation and without sintering to isotropic or anisotropic magnets with high Coercivity and maximum energy product can be processed.
• This aim is achieved according to the invention by combining the following process steps, that the starting alloy present in pieces or in the form of ingots is crushed, the powder particles thus obtained are heat-treated to improve their magnetic properties, preferably in a temperature range of 300-1000 ° C., and then the The surface of the individual heat-treated powder particles is coated with a ceramic or metallic protective layer to prevent corrosion, the metallic coating preferably being carried out electrolytically from an aqueous solution.
• the powders produced by the process according to the invention can then, if appropriate with the addition of a pressing aid, be processed by simple pressing, if appropriate with application of an external magnetic field, to permanent magnets with excellent properties.
• the invention also relates to a magnet made of hard magnetic powder, which is characterized in that the powder particles consist of an alloy containing 25-45% by weight SE, 0.5-3% by weight B and iron or a combination of iron contains at least one other metal from the group cobalt, aluminum and niobium and are coated with a ceramic or metallic protective layer.
• the invention also relates to a method for Production of such a magnet, which consists in that the coated powder is optionally pressed into magnets under the action of an external magnetic field, the pressing preferably taking place with the addition of a plastic, a metal or ceramic powder to improve the strength of the compact.
• the addition of other rare earths can increase certain properties, such as the coercive field strength.
• Another component of the alloy is boron, which is necessary to form the hard magnetic phase and is present in quantities of 0.5-3% by weight.
• the remainder of the alloy is iron or a combination of iron with another element, e.g. Cobalt, aluminum, niobium or others. The combination of iron with these elements can lead to an improvement in temperature resistance and magnetic properties.
• the starting alloy is produced by the molten metal-lurgic route, it being of the utmost importance that the oxygen content be kept as low as possible so that the prerequisite for the production of the lowest possible oxygen powder is given.
• An improvement in the magnetic properties of an atomized powder can be achieved if the alloy droplets move through a magnetic field during the atomization process and solidify in it. If the atomized alloy is ground briefly before the heat treatment, for example in a stirred ball mill under liquid, to an FSSS value of ⁇ 30 ⁇ m, preferably 15-3 ⁇ m, a magnetically anisotropic material is obtained, which also has a low oxygen content. Compared to the powders produced by the known "melt spinning" process with subsequent grinding, this comminution method is advantageous since the particles are also partially spherical after grinding and can therefore be coated more easily. To explain the importance of oxygen, Table 1 shows the oxygen contents of dry powders of an NdFeB alloy, which were finely divided for two hours and stored in air to determine 02 uptake, depending on the grain size.
• Another necessary step in the manufacturing process according to the invention is the heat treatment of the powders.
• the powders are transferred directly into a vacuum oven under solvent or in an inert gas atmosphere and subjected to heat treatment between 300 ° and 1000 ° C in one or more stages.
• a heat treatment of the powder for example, increased the coercive field strength of a ground alloy with an FSSS value of 5 ⁇ m from 222.9 kA / m in the original material to 802 kA / m, which represents a significant improvement.
• the production of the magnetic powder in the manner described is the prerequisite for achieving good magnetic properties.
• a prerequisite for the corrosion resistance of the powder is a complete coating of the individual powder particles with a metallic or ceramic material.
• a metal is deposited, for example, by an electrolytic process, as in the case of electrodeless coating with copper, which is described below:
• An aqueous solution of copper sulfate, sodium hydroxide solution and potassium sodium tartrate is prepared, the alloy is stirred in and formaldehyde is added. The copper is deposited metallically on the surface of the powder.
• the proportion of coating material varies depending on the fineness of the powder and the surface associated with it. It is between 10 and 25% for the previously described grain sizes. Just By applying a corrosion-resistant layer to each individual powder particle, however, there is sufficient resistance to corrosion of the powder and the magnets.
• a lumpy NdFeB alloy with the following composition 33.3% SE (in 100% SE 98.7% Nd) 1.3% B 65.2% Fe 0.04% O was melted under an inert gas atmosphere, then atomized and a fraction ⁇ 63 ⁇ m was sieved out. It was then heat-treated at 630 ° C and then coated with copper without electrodes. For this purpose, the atomized and heat-treated alloy was stirred into an aqueous solution which contained 30 g / l CuSo4, 80 g / l 60% NaOH and 150 g / l KNa tartrate. Then 1 part by volume of 37% formaldehyde was added to 5 parts by volume of this solution. After the Cu had been deposited and the coated alloy had been filtered, it was washed thoroughly. It contained 13.2% Cu and 0.17% oxygen. Table 2 shows the values for the coercive field strength for the individual intermediates and the end material.
• Example 2 A lumpy NdFeB alloy with the same composition as in Example 1 was melted under an inert gas atmosphere, atomized and the atomized material was ground under cyclohexane to an FSSS value of 5.2 ⁇ m in an attritor. The powder was placed in a vacuum oven while wet with solvent and heat-treated at 630 ° C. The coating was again carried out according to Example 1 and the powder had a copper content of 18.2% and an oxygen content of 0.27% O. Table 3 again summarizes the coercive field strengths.

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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)

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• 1986
  • 1986-08-04 AT AT209386A patent/AT386554B/de not_active IP Right Cessation
• 1987
  • 1987-07-28 JP JP62186775A patent/JPS6338216A/ja active Pending
  • 1987-07-31 EP EP87890182A patent/EP0255816A3/fr not_active Withdrawn

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