Abstract: The present invention aims to provide a NdFeB system sintered magnet capable of improving the magnetization characteristic. The NdFeB system sintered magnet is a NdFeB system sintered magnet with the c axis oriented in one direction, characterized in that: the median of the grain size of the crystal grains at a section perpendicular to the c axis is 4.5 ?m or less, and the area ratio of the crystal grains having grain sizes of 1.8 ?m or smaller on the aforementioned section is 5% or lower. The median of the grain size is decreased (to 4.5 ?m or less), whereby improve the coercive force is improved. Simultaneously, the area ratio of the crystal grains having grain sizes of 1.8 ?m or smaller is decreased (to 5% or lower) to reduce the number of crystal grains having no magnetic wall formed, whereby the magnetization characteristic is improved.

Abstract: A NdFeB system sintered magnet produced by the grain boundary diffusion method that has a high coercive force and squareness ratio with only a small decrease in the maximum energy product. The NdFeB system sintered magnet has a base material produced by orienting powder of a NdFeB system alloy and sintering the powder, with Dy and/or Tb (the “Dy and/or Tb” is hereinafter called RH) attached to and diffused from a surface of the base material through the grain boundary inside the base material by a grain boundary diffusion treatment, wherein the difference Cs-Cd3 between the RH content Cs (wt %) in the grain boundary reaching the surface to which RH is attached and the RH content Cd3 (wt %) in the grain boundary at a depth of 3 mm from the aforementioned attachment surface is equal to or smaller than 20 wt %.

Abstract: A NdFeB system sintered magnet produced by the grain boundary diffusion method and has a high coercive force and squareness ratio with only a small decrease in the maximum energy product. A NdFeB system sintered magnet having a base material produced by orienting powder of a NdFeB system alloy and sintering the powder, with Dy and/or Tb (the “Dy and/or Tb” is hereinafter called RH) attached to and diffused from a surface of the base material through the grain boundary inside the base material by a grain boundary diffusion treatment, wherein the difference Cgx?Cx between the RH content Cgx (wt %) in the grain boundary and the RH content Cx (wt %) in main-phase grains which are grains constituting the base material at the same depth within a range from the surface to which RH is attached to a depth of 3 mm is equal to or larger than 3 wt %.

Abstract: A method for producing a NdFeB system sintered magnet. The method includes: a hydrogen pulverization process, in which coarse powder of a NdFeB system alloy is prepared by coarsely pulverizing a lump of NdFeB system alloy by making this lump occlude hydrogen; a fine pulverization process, in which fine powder is prepared by performing fine pulverization for further pulverizing the coarse powder; a filling process, in which the fine powder is put into a filling container; an orienting process, in which the fine powder in the filling container is oriented; and a sintering process, in which the fine powder after the orienting process is sintered as held in the filling container. The processes from hydrogen pulverization through orienting are performed with neither dehydrogenation heating nor evacuation each for desorbing hydrogen occluded in the hydrogen pulverization process. The processes from hydrogen pulverization through sintering are performed in an oxygen-free atmosphere.

Abstract: An RFeB system sintered magnet wherein heavy rare-earth element RH which is at least one kind of rare-earth element selected from Dy, Tb and Ho is diffused into base material through the grain boundaries of base material made of a sintered compact of an RFeB system magnet containing RL, Fe and B, where RL represents a light rare-earth element which is at least one kind of rare-earth element selected from Nd and Pr, wherein: size of the RFeB system sintered magnet at smallest-size portion is greater than 3 mm; the amount of heavy rare-earth element RH contained in RFeB system sintered magnet divided by volume of RFeB system sintered magnet is ?25 mg/cm3; and the difference between local coercivity at the surface of the smallest-size portion and in the central region of the smallest-size portion is equal to or less than 15% of local coercivity at the surface.

Abstract: A NdFeB system sintered magnet produced by the grain boundary diffusion method and has a high coercive force and squareness ratio with only a small decrease in the maximum energy product. A NdFeB system sintered magnet having a base material produced by orienting powder of a NdFeB system alloy and sintering the powder, with Dy and/or Tb (the “Dy and/or Tb” is hereinafter called RH) attached to and diffused from a surface of the base material through the grain boundary inside the base material by a grain boundary diffusion treatment, wherein the difference Cgx-Cx between the RH content Cgx (wt %) in the grain boundary and the RH content Cx (wt %) in main-phase grains which are grains constituting the base material at the same depth within a range from the surface to which RH is attached to a depth of 3 mm is equal to or larger than 3 wt %.

Abstract: A NdFeB system sintered magnet produced by the grain boundary diffusion method and has a high coercive force and squareness ratio with only a small decrease in the maximum energy product. A NdFeB system sintered magnet having a base material produced by orienting powder of a NdFeB system alloy and sintering the powder, with Dy and/or Tb (the “Dy and/or Tb” is hereinafter called RH) attached to and diffused from a surface of the base material through the grain boundary inside the base material by a grain boundary diffusion treatment, wherein the difference Cgx-Cx between the RH content Cgx (wt %) in the grain boundary and the RH content Cx (wt %) in main-phase grains which are grains constituting the base material at the same depth within a range from the surface to which RH is attached to a depth of 3 mm is equal to or larger than 3 wt %.

Abstract: A NdFeB system sintered magnet according to the present invention is a NdFeB system sintered magnet having a base material produced by orienting powder of a NdFeB system alloy and sintering the powder, with Dy and/or Tb (the “Dy and/or Tb” is hereinafter called RH) attached to and diffused from a surface of the base material through the grain boundary inside the base material by a grain boundary diffusion treatment, wherein the number of grain-boundary triple points at which the difference Ct?Cw between the RH content Ct (wt %) at the grain-boundary triple point and the RH content Cw (wt %) at a two-grain boundary portion leading to that grain-boundary triple point is equal to or smaller than 4 wt % is equal to or larger than 60% of the total number of grain-boundary triple points.

Abstract: A NdFeB system sintered magnet according to the present invention is a NdFeB system sintered magnet having a base material produced by orienting powder of a NdFeB system alloy and sintering the powder, with Dy and/or Tb (the “Dy and/or Tb” is hereinafter called RH) attached to and diffused from a surface of the base material through the grain boundary inside the base material by a grain boundary diffusion treatment, wherein the number of grain-boundary triple points at which the difference Ct?Cw between the RH content Ct (wt %) at the grain-boundary triple point and the RH content Cw (wt %) at a two-grain boundary portion leading to that grain-boundary triple point is equal to or smaller than 4 wt % is equal to or larger than 60% of the total number of grain-boundary triple points.

Abstract: A sintered magnet production system using a press-less method capable of minimizing the distortion of a sintered magnet includes: a filling device for filling a container cavity with alloy powder for a sintered magnet; an orienting section for orienting the powder in the cavity by applying a magnetic field without applying a mechanical pressure to the powder; and a sintering section for sintering the powder oriented by the orienting section, by heating the powder without applying a mechanical pressure to the powder. The orienting section includes: an air-core coil; and two ferromagnetic members made of a ferromagnetic material arranged within the coil at respective open ends of the coil with a space for containing the container in between. The ferromagnetic members adjust the magnetic field within the coil toward a direction parallel to the axis of the coil, whereby distortion of a sintered magnet is minimized.

Abstract: The present invention aims to provide a NdFeB system sintered magnet capable of improving the magnetization characteristic. The NdFeB system sintered magnet is a NdFeB system sintered magnet with the c axis oriented in one direction, characterized in that: the median of the grain size of the crystal grains at a section perpendicular to the c axis is 4.5 ?m or less, and the area ratio of the crystal grains having grain sizes of 1.8 ?m or smaller on the aforementioned section is 5% or lower. The median of the grain size is decreased (to 4.5 ?m or less), whereby improve the coercive force is improved. Simultaneously, the area ratio of the crystal grains having grain sizes of 1.8 ?m or smaller is decreased (to 5% or lower) to reduce the number of crystal grains having no magnetic wall formed, whereby the magnetization characteristic is improved.

Abstract: Provided is a NdFeB sintered magnet which can be used in the grain boundary diffusion method as a base material in which RH can be easily diffused through the rare-earth rich phase and which itself has a high coercive force, a high maximum energy product and a high squareness ratio, as well as a method for producing such a magnet. A NdFeB system sintered has an average grain size of the main-phase grains magnet is equal to or smaller than 4.5 ?m, the carbon content of the entire NdFeB system sintered magnet is equal to or lower than 1000 ppm, and the percentage of the total volume of a carbon rich phase in a rare-earth rich phase at a grain-boundary triple point in the NdFeB system sintered magnet to the total volume of the rare-earth rich phase is equal to or lower than 50%.

Abstract: A method for producing a NdFeB system sintered magnet. The method includes: a hydrogen pulverization process, in which coarse powder of a NdFeB system alloy is prepared by coarsely pulverizing a lump of NdFeB system alloy by making this lump occlude hydrogen; a fine pulverization process, in which fine powder is prepared by performing fine pulverization for further pulverizing the coarse powder; a filling process, in which the fine powder is put into a filling container; an orienting process, in which the fine powder in the filling container is oriented; and a sintering process, in which the fine powder after the orienting process is sintered as held in the filling container. The processes from hydrogen pulverization through orienting are performed with neither dehydrogenation heating nor evacuation each for desorbing hydrogen occluded in the hydrogen pulverization process. The processes from hydrogen pulverization through sintering are performed in an oxygen-free atmosphere.

Abstract: The NdFeB system sintered magnet according to the present invention is a NdFeB system sintered magnet produced by diffusing Dy and/or Tb which are/is attached to a surface of a base material produced by orienting powder of a NdFeB system alloy in a magnetic field, and sintering the powder of the NdFeB system alloy, into grain boundaries inside the base material by grain boundary diffusion treatment, wherein a squareness ratio is equal to or higher than 95%. The NdFeB system sintered magnet can be produced by producing a base material of the NdFeB system sintered magnet by using a NdFeB system alloy with lamellas of a rare-earth rich phase dispersed substantially uniformly at predetermined spaces, as a starting alloy, and causing the alloy to occlude hydrogen, without performing heating for desorbing the occluded hydrogen thereafter until a sintering process, and applying grain boundary diffusion treatment to the base material.

Abstract: A method for producing a NdFeB system sintered magnet in which a coating material containing a heavy rare-earth element RH applied to a base material of a NdFeB system sintered magnet is inexpensively prevented from adhering to a tray or similar device in a grain boundary diffusion treatment. The method includes the steps of applying a coating material containing a heavy rare-earth element RH to a base material and diffusing the element through grain boundaries in the base material by a grain boundary diffusion method. The coating material is applied to a sheet. The sheet is made to come in tight contact with the base material so that the coating material applied to the sheet contacts an application target surface of the base material. With the sheet held in tight contact with the base material, the grain boundary diffusion treatment (heat treatment) is performed on the base material.

Abstract: Provided is a NdFeB sintered magnet which can be used in the grain boundary diffusion method as a base material in which RH can be easily diffused through the rare-earth rich phase and which itself has a high coercive force, a high maximum energy product and a high squareness ratio, as well as a method for producing such a magnet. A NdFeB system sintered has an average grain size of the main-phase grains magnet is equal to or smaller than 4.5 ?m, the carbon content of the entire NdFeB system sintered magnet is equal to or lower than 1000 ppm, and the percentage of the total volume of a carbon rich phase in a rare-earth rich phase at a grain-boundary triple point in the NdFeB system sintered magnet to the total volume of the rare-earth rich phase is equal to or lower than 50%.

Abstract: A NdFeB system sintered magnet according to the present invention is a NdFeB system sintered magnet having a base material produced by orienting powder of a NdFeB system alloy and sintering the powder, with Dy and/or Tb (the “Dy and/or Tb” is hereinafter called RH) attached to and diffused from a surface of the base material through the grain boundary inside the base material by a grain boundary diffusion treatment, wherein the number of grain-boundary triple points at which the difference Ct-Cw between the RH content Ct (wt %) at the grain-boundary triple point and the RH content Cw (wt %) at a two-grain boundary portion leading to that grain-boundary triple point is equal to or smaller than 4 wt % is equal to or larger than 60% of the total number of grain-boundary triple points.

Abstract: A NdFeB system sintered magnet produced by the grain boundary diffusion method and has a high coercive force and squareness ratio with only a small decrease in the maximum energy product. A NdFeB system sintered magnet having a base material produced by orienting powder of a NdFeB system alloy and sintering the powder, with Dy and/or Tb (the “Dy and/or Tb” is hereinafter called RH) attached to and diffused from a surface of the base material through the grain boundary inside the base material by a grain boundary diffusion treatment, wherein the difference Cgx-Cx between the RH content Cgx (wt %) in the grain boundary and the RH content Cx (wt %) in main-phase grains which are grains constituting the base material at the same depth within a range from the surface to which RH is attached to a depth of 3 mm is equal to or larger than 3 wt %.

Abstract: A NdFeB system sintered magnet produced by the grain boundary diffusion method that has a high coercive force and squareness ratio with only a small decrease in the maximum energy product. The NdFeB system sintered magnet has a base material produced by orienting powder of a NdFeB system alloy and sintering the powder, with Dy and/or Tb (the “Dy and/or Tb” is hereinafter called RH) attached to and diffused from a surface of the base material through the grain boundary inside the base material by a grain boundary diffusion treatment, wherein the difference Cs-Cd3 between the RH content Cs (wt %) in the grain boundary reaching the surface to which RH is attached and the RH content Cd3 (wt %) in the grain boundary at a depth of 3 mm from the aforementioned attachment surface is equal to or smaller than 20 wt %.

Abstract: A method and system for producing a slim-shaped sintered NdFeB magnet having a high level of coercive force and high degree of orientation, as well as a sintered NdFeB magnet produced by the aforementioned method or system. A system for producing a slim-shaped sintered NdFeB magnet according to the present invention includes: a filling unit and filling alloy powder; an orienting unit; a sintering furnace; and a conveying unit. The orienting unit is provided with a heating and orienting coil for heating the alloy powder in the molds before and/or after the application of the magnetic field so as to decrease the coercive force of the individual particles of the alloy powder.