1010 results about "Sintered magnets" patented technology

In a method for producing an R—Fe—B based rare-earth sintered magnet according to the present invention, first, provided is an R—Fe—B based rare-earth sintered magnet body including, as a main phase, crystal grains of an R₂Fe₁₄B type compound that includes a light rare-earth element RL, which is at least one of Nd and Pr, as a major rare-earth element R. Thereafter, the sintered magnet body is heated while a heavy rare-earth element RH, which is at least one element selected from the group consisting of Dy, Ho and Tb, is supplied to the surface of the sintered magnet body, thereby diffusing the heavy rare-earth element RH into the rare-earth sintered magnet body.

An alloy for R-T-B-based rare earth sintered magnets which contains R which is a rare earth element; T which is a transition metal essentially containing Fe; a metallic element M containing one or more metals selected from Al, Ga and Cu; B and inevitable impurities, in which R accounts for 13 at % to 15 at %, B accounts for 4.5 at % to 6.2 at %, M accounts for 0.1 at % to 2.4 at %, T accounts for balance, a proportion of Dy in all rare earth elements is in a range of 0 at % to 65 at %, and the following Formula 1 is satisfied,

0.0049Dy+0.34≦B/TRE≦0.0049Dy+0.36  Formula 1

wherein Dy represents a concentration (at %) of a Dy element, B represents a concentration (at %) of a boron element, and TRE represents a concentration (at %) of all the rare earth elements.

Disclosed is a method of preparing a micro-structured powder for bonded magnets having high coercivity, which is advantageous in terms of low preparation costs by recycling magnet scraps, simplified mass production, minimal environmental contamination by such a recycling process, and the preparation of stable anisotropic powders having high coercivity. Further, a magnet powder prepared by the above method is provided. The current method is characterized in that R—Fe—B type anisotropic sintered magnets or scraps thereof are crushed to prepare 50-500 μm sized magnet powders, which are then mixed with 1-10 wt % of rare earth fluoride (RF₃) powders and thermally treated at high temperatures (500-1100° C.) in a vacuum or an inert gas, to cause the change of matrix-near surface and grain boundary of the powders. Thus obtained powders include a matrix phase having R₂Fe₁₄B crystal structure, a R-rich grain boundary phase containing rare earth fluoride, and other phases, in which the matrix phase has an average grain size of 1-20 μm, and the powders have an average size of 50-500 μm with superior magnetic characteristics of (BH)max≧20 MGOe and iHc≧5 kOe.

In a rotating machine comprising a rotor including a rotor core and a plurality of permanent magnet segments, and a stator including a stator core and windings, the permanent magnet segment is obtained by disposing a powder comprising an R² oxide, R³ fluoride or R⁴ oxyfluoride on a sintered magnet body of R¹—Fe—B composition, wherein R¹ to R⁴ are rare earth elements, and heat treating the powder-covered magnet body. The permanent magnet segment of a cross-sectional shape which is tapered from the center toward opposed ends has a higher coercive force at the ends than at the center.

A rare earth permanent magnet is prepared from a sintered magnet body of a R¹—Fe—B composition wherein R¹ is a rare earth element inclusive of Y and Sc, by forming a plurality of slits in a surface of the magnet body, disposing a powder on the magnet body surface, the powder comprising an oxide of R², a fluoride of R³, or an oxyfluoride of R⁴ wherein each of R², R³, and R⁴ is a rare earth element, and heat treating the magnet body and the powder below the sintering temperature in vacuum or in an inert gas.

The present invention relates to a magnet powder formula of hexagonal type magnetoplumbite permanent magnetic ferrite, sintered magnet and method of producing the same. The invention provides a sintered permanent magnetic ferrite and magnet powder capable of acquiring remanence of more than 4500 Gs and Intrinsic coercivity of more than 5000 Oe at the same time, pointing to problems of unable to acquire high magnetic property and high Intrinsic coercivity at the same time in prior technology, and method of producing the same. major formula of the invention is a permanent magnetic ferrite powder containing hexagonal type magnetoplumbite permanent magnetic ferrite of the following formula as main phase: A[1-x-y]Ca[x]R[y]Fe[2n-z]M[z]O[19], A represents Sr or Sr and Ba, R represents at least one of La, Pr, Nd or Bi, and La is needed; M represents at least one of Co, Ni and Zn, and Co is needed; x, y, z represents addition percentage of each main metal elements.

In a method for producing an R-Fe-B rare earth sintered magnet, there is firstly prepared an R-Fe-B rare earth sintered magnet body which contains, as the main phase, R2Fe14B compound crystal grains containing a light rare earth element RL (at least one of Nd and Pr) as a main rare earth element R, and then a heavy rare earth element RH is diffused into the rare earth sintered magnet body from the surface thereof by heating the sintered magnet body while supplying the heavy rare earth element RH (at least one substance selected from the group consisting of Dy, Ho and Tb) to the surface of the sintered magnet body.

A ferrite magnetic material and ferrite sintered magnet composed thereof have a ferrite having a hexagonal crystal structure as a main component. A composition ratio of a metallic element included in the main component is represented by: R_xA_1-x(Fe_12-yCo_y)_z. R is at least one element selected from La, Ce, Pr, Nd and Sm and at least includes La. A is at least two elements selected from Ca, Sr and Ba and at least includes Ca and Sr. Si component and either or both of Al component and Cr component are included as a sub-component. When a sum of Al content and a value obtained by dividing Cr content by four and a value obtained by calculating the formula [(R+A)−(Fe+Co)/12]/Si where R, A, Fe, Co and Si indicate values of each atom % thereof are defined as L and G, respectively, L and G have to be values within a predetermined region.

The invention discloses a method for preparing a heavy rare earth hydride nano-particle doped sintered NdFeB permanent magnet, which belongs to the technical field of magnetic materials. The prior preparation method improves the coercive force and the temperature stability of magnets by adding heavy rare earth elements, namely terbium or dysprosium into master alloy, but the method can cause the residual magnetism of the magnets, the reduction of magnetic energy product and the increase of manufacturing cost. The method adopts heavy rare earth terbium hydride and dysprosium hydride nano-powder doping technology to prepare the sintered NdFeB permanent magnet with high coercive force and excellent magnetic property. The method comprises the following steps: preparing NdFeB powder by a rapidly solidified flake process and a hydrogen decrepitation process; preparing the terbium hydride or the dysprosium hydride nano-powder by physical vapor deposition technology; mixing the two powders, and performing magnetic field orientation and press forming; and performing dehydrogenation treatment, sintering and heat treatment on a green compact at different temperatures, and obtaining the sintered magnet. The coercive force of the magnet prepared by the method is higher than that of the prior sintered magnet with the same ingredients; and compared with the sintered magnet with the equivalent coercive force, the proportion of the terbium and dysprosium needed by the magnet prepared by the method is remarkably reduced.

The object of the present invention is to provide rare-earth system sintered magnets such as R-Fe-B system or R-Co system having excellent magnetic properties, unique configuration of a small size, thin wall thickness and intricate geometry. With the method for preparing the present invention, a granulation of alloy powders can be achieved easily, a chemical reaction between rare-earth system and binder substances can be suppressed, so that the residual oxygen and carbon levels in the sintered products can be reduced. Moreover, by this production method, the flowability and lubricant capability during the forming process can be improved. The dimension accuracy and productivity are also enhanced. A certain type of binder is added to rare-earth alloy powders and kneaded into a slurry state. The slurry is then formed into granulated powders by spray-dryer equipment. The thus granulated powders are molded, and sintered through a powder metallurgy technique.

The present invention provides an oxide magnetic material, which includes a primary phase of a hexagonal ferrite containing metallic elements Ca, R, Fe and M, where M represents at least one element selected from the group including Co, Ni and Zn, and R represents at least one element selected from the group including Bi and rare earth elements including Y, with La being essentially included in R; wherein the proportions of the metallic elements Ca, R, Fe and M with respect to the total amount of the metallic elements are from 1 to 13 atomic % for Ca, from 0.05 to 10 atomic % for R, from 80 to 95 atomic % for Fe, and from 1 to 7 atomic % for M. The present invention also provides ferrite particles, a bonded magnet, a sintered magnet, a process for producing them, and a magnetic recording medium, which contain the oxide magnetic material.

The invention discloses a 2:17 type samarium-cobalt sintered magnet material and a preparation method thereof. The 2:17 type samarium-cobalt sintered magnet material comprises the following raw materials in percentage by mass: 10 to 25 percent of samarium, 45 to 55 percent of cobalt, 10 to 20 percent of iron, 3 to 9 percent of copper, 1 to 3 percent of zirconium and 5 to 15 percent of at least one heavy rear earth element. Due to the selection and the proportion of the raw materials and the innovation of the sintering process, a microstructure of the magnet material is optimized, and the aims of reducing the temperature coefficient of a magnet and simultaneously maintaining higher magnetic energy product of the magnet are fulfilled, wherein the magnetic energy product of the prepared magnet is 14 to 25 MGsOe, the residual magnetism temperature coefficient is about -0.005 to -0.03 percent per DEG C, and a lower magnetic flux temperature coefficient is maintained in an environment at the temperature of between -35 and 300 DEG C.

The invention discloses a high-obdurability Nd-Fe-B sintered magnet reconstructed by the grain boundary phase and the preparation method thereof. The Nd-Fe-B sintered magnet comprises the component of NdeFe100-e-f-gBfMg, wherein, e is more than or equal to 6 and less than or equal to 24, f is more than or equal to 5.3 and less than or equal to 6.4, and g is more than or equal to 0.01 and less than or equal to 6, and M is one or more elements of Dy, Tb, Pr, Sm, Ce, Yb, Co, Ni, Mn, Nb, Ta, Zr, Si, Ti, Mo, Ag, Au, Mg, Cu, Al, Zn, Ga, Bi, Sn and In; the preparation method comprises the following steps: main phase alloy and grain boundary phase alloy are respectively prepared into powder, and then the powder is intensively mixed; the mixed powder is pressed into the molded blank in the magnetic field; and the sintered magnet is obtained in a high-vacuum sintering oven. Through the restruction of the grain boundary phase component, the solution grain boundary phase alloy with low smelting point and high strength ductility is achieved, the obdurability of the grain boundary phase is enhanced on the basis that the magnetic property is guaranteed, thereby the high ductility of the magnet is enhanced, and the process is simple, the cost is low, and the magnet is suitable for the mass production, thereby the double-alloy method combined with the grain boundary restruction can be used for preparing the Nd-Fe-B sintered magnet with high obdurability.

[Problem] In known methods, an improvement of the coercive force is realized by allowing the Dy metal or the like to present selectively in crystal grain boundary portions of a sintered magnet. However, since these are based on a physical film formation method, e.g., sputtering, through the use of a vacuum vessel, there is a mass productivity problem in the case where large amounts of magnet is treated. Furthermore, there is a magnet cost problem from the viewpoint that, for example, an expensive, high-purity Dy metal or the like must be used as a raw material for film formation.

[Solving Means] A method for modifying grain boundaries of a Nd—Fe—B base magnet characterized by including the step of allowing an M metal component to diffuse and penetrate from a surface of a Nd—Fe—B base sintered magnet body having a Nd-rich crystal grain boundary phase surrounding principal Nd₂Fe₁₄B crystals to the grain boundary phase through a reduction treatment of a fluoride, an oxide, or a chloride of an M metal element (where M is Pr, Dy, Tb, or Ho).

The method includes steps: (1) using casting technique to produce ingot of Nd-Fe-B alloy, or using quick hardening technique to produce quick hardening slices; (2) using hydrogen explosion technique or crusher to crash alloy of ingot or quick hardening slices into coarse powder; (3) through airflow grinding machine to produce fine powder from coarse powder; and mixed compressed gas from nitrogen and hydrogen is adopted by the airflow grinding machine; (4) mixing fine powder, gasoline, and antioxidant evenly by blender so as to obtain mixed powder; (5) molded blanks are pressed from mixed powder under 1.2-2.0T magnetic field; (6) molded blanks are sintered inside high vacuum sintering furnace at deg.C 1050-1120 for 2-4h; and through temper of heat treatment 2-4h at deg.C 500-650 so as to produce sintered magnet. Comparing with traditional technique, the invention produces magnet with high coercive force, and fine powder in high efficiency, is suitable to batch production.

A permanent magnet is provided which has formed a Dy, Tb film on a surface of an iron-boron-rare earth sintered magnet of a predetermined shape, with diffusion thereof into grain boundary phases, having a higher coercive force. The method of manufacturing a permanent magnet includes a film-forming step of evaporating metal evaporating material containing at least one of Dy and Tb and adhering evaporated metal atoms to a surface of the iron-boron-rare earth sintered magnet, and a diffusing step of performing heat treatment to diffuse metal atoms adhered to the surface into grain boundary phases of the sintered magnet. The metal evaporating material contains at least one of Nd and Pr.

An R-T-B system sintered magnet is provided which achieves both a high residual magnetic flux density and a high coercive force. The R-T-B system sintered magnet comprises main-phase grains 1 each having a core-shell structure comprising an inner shell part 2 and an outer shell part 3 surrounding the inner shell part 2, wherein the concentration of the heavy rare earth element in the inner shell part 2 is lower by 10% or more than the concentration of the heavy rare earth element in the periphery of the outer shell part 3, and (L/r)_ave falls within a range from 0.03 to 0.40 in the main-phase grains 1 each comprising the inner shell part 2 and the outer shell part 3, wherein L represents the shortest distance from the periphery of the main phase grain 1 to the inner shell part 2, r represents the equivalent diameter of the main phase grain 1, and (L/r)_ave represents the average value of L/r for the main-phase grains 1 present in the sintered body and having the core-shell structure.

A sintered ferrite magnet having a basic composition represented by the general formula: A_1−x−y+aCa_x+bR_y+cFe_2n−zCo_z+dO₁₉ (atomic ratio), wherein a, b, c and d represent the amounts of an A element, Ca, an R element and Co added in the pulverization step of an oxide magnet material, which are numerals meeting the conditions of 0.03≦x≦0.4, 0.1≦y≦0.6, 0≦z≦0.4, 4≦n≦10, x+y≦1, 0.03≦x+b≦0.4, 0.1≦y+c≦0.6, 0.1≦z+d≦0.4, 0.50≦[(1−x−y+a)/(1−y+a+b)]≦0.97, 1.1≦(y+c)/(z+d)≦1.8, 1.0≦(y+c)/x≦20, and 0.1≦x/(z+d)≦1.2.