Rotating Machine with Sintered Magnet and Method for Producing Sintered Magnet

Abstract

A rotating machine is equipped with a sintered magnet. The sintered magnet includes: a ferromagnetic material consisting mainly of iron; a layer of a fluoride compound or a layer of an oxyfluoride compound formed inside crystal grains or in a portion of grain boundary area of the ferromagnetic material; at least one element selected from the group consisting of alkalis, alkaline earth elements, and rare earth elements and carbon contained in the layer of the fluoride compound or the layer of the oxyfluoride compound; and a continuously extending layer formed by a portion of the layer of the fluoride compound or the layer of the oxyfluoride layer, the continuously extending layer extending from a surface of the ferromagnetic material through the inside of the ferromagnetic material to an opposite side surface of the ferromagnetic material. A ratio of an average concentration of fluorine in an area within 100 μm from the surface of the ferromagnetic material to an average concentration of fluorine in an area including a central part at a distance of at least 100 μm is in the range of 1±0.5, and a concentration gradient of the rare earth elements is present in a matrix near the grain boundary of the ferromagnetic material.

1 . A rotating machine equipped with a sintered magnet, the sintered magnet comprising:
 a ferromagnetic material consisting mainly of iron;   a layer of a fluoride compound or a layer of an oxyfluoride compound formed inside crystal grains or in a portion of grain boundary area of the ferromagnetic material;   at least one element selected from the group consisting of alkalis, alkaline earth elements, and rare earth elements and carbon contained in the layer of the fluoride compound or the layer of the oxyfluoride compound; and   a continuously extending layer formed by a portion of the layer of the fluoride compound or the layer of the oxyfluoride layer, the continuously extending layer extending from a surface of the ferromagnetic material through the inside of the ferromagnetic material to an opposite side surface of the ferromagnetic material, wherein   a ratio of an average concentration of fluorine in an area within 100 μm from the surface of the ferromagnetic material to an average concentration of fluorine in an area including a central part at a distance of at least 100 μm is in the range of 1±0.5, and   a concentration gradient of the rare earth elements is present in a matrix near the grain boundary of the ferromagnetic material.   
     
     
         2 . A rotating machine equipped with a sintered magnet, the sintered magnet comprising:
 a ferromagnetic material consisting mainly of iron and a rare earth element;   a fluoride compound or an oxyfluoride compound formed inside crystal grains or in a portion of grain boundary area of the ferromagnetic material;   at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements and carbon contained in the fluoride compound or the oxyfluoride compound; and   a continuously extending layer formed by a portion of the fluoride compound or the oxyfluoride, the continuously extending layer extending from a surface of the ferromagnetic material through the inside of the ferromagnetic material to an opposite side surface of the ferromagnetic material, wherein   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates along the continuously extending layer, and   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates inside grains of the fluoride compound or the oxyfluoride compound.   
     
     
         3 . A rotating machine equipped with a sintered magnet, the sintered magnet comprising:
 a ferromagnetic material consisting mainly of iron and a rare earth element;   a fluoride compound or an oxyfluoride compound formed inside crystal grains or in a portion of grain boundary area of the ferromagnetic material;   at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements and carbon contained in the fluoride compound or the oxyfluoride compound; and   a continuously extending layer formed by the fluoride compound or the oxyfluoride, the continuously extending layer extending from a surface of the ferromagnetic material through the inside of the ferromagnetic material to an opposite side surface of the ferromagnetic material, wherein   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates along the continuously extending layer and along the grain boundary of the ferromagnetic material, and grains of the fluoride compound or the oxyfluoride compound are formed,   the at least one element selected from the group consisting of alkalis alkaline earth elements, metal elements, and rare earth elements segregates in an increasing concentration from a center of the grain toward outside thereof in a portion of the grains of the fluoride compound or the oxyfluoride compound, and   an average concentration of fluorine or carbon measured over an area not smaller than 100 μm 2  is such that a ratio of a value measured in an area within 100 μm from an outermost surface of the ferromagnetic material to a value measured in an area including a central part at a distance of not smaller than 100 μm from the outermost surface is 1±0.5.   
     
     
         4 . A rotating machine equipped with a sintered magnet, the sintered magnet comprising:
 a ferromagnetic material consisting mainly of iron and a rare earth element;   at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements and carbon contained in the fluoride compound or the oxyfluoride compound; and   a continuously extending layer formed by the fluoride compound or the oxyfluoride, the continuously extending layer extending in a grain boundary at any locus of the ferromagnetic material without being connected to an outermost surface of the ferromagnetic material, wherein   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates along the continuously extending layer and along a grain boundary of a matrix of the ferromagnetic material, and   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates within grains of the fluoride compound or the oxyfluoride compound having a crystal structure with n-fold symmetry in an increasing concentration from a center of the grain toward outside thereof.   
     
     
         5 . A rotating machine equipped with a sintered magnet, the sintered magnet comprising:
 a ferromagnetic material consisting mainly of iron and a rare earth element;   a fluoride compound or an oxyfluoride compound formed inside crystal grains or in a portion of grain boundary area of the ferromagnetic material;   at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements and carbon contained in the fluoride compound or the oxyfluoride compound; and   a continuously extending layer formed by the fluoride compound or the oxyfluoride, the continuously extending layer extending from a surface of the ferromagnetic material through the inside of the ferromagnetic material to an opposite side surface of the ferromagnetic material, wherein   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates in an outer peripheral portion within the grain along the continuously extending layer and along the grain boundary of the ferromagnetic material, and grains of the fluoride compound or the oxyfluoride compound are formed,   there are present in a portion of the grains of the fluoride compound or the oxyfluoride compound a gradient of concentration in which the at least one element selected from the group consisting of alkalis alkaline earth elements, metal elements, and rare earth elements is in an increasing concentration from a center of the grain toward an outer side of the grain and a gradient of concentration in which the at least one element selected from the group consisting of alkalis alkaline earth elements, metal elements, and rare earth elements is in a decreasing concentration from a center of the grain toward the outer side of the grain in a portion of the grains of the fluoride compound or the oxyfluoride compound, and an average concentration of fluorine or carbon measured over an area not smaller than 100 μm 2  is such that a ratio of a value measured in an area within 100 μm from an outermost surface of the ferromagnetic material to a value measured in an area including a central part at a distance of not smaller than 100 μm from the outermost surface is 1±0.5.   
     
     
         6 . A rotating machine equipped with a sintered magnet, the sintered magnet comprising:
 a ferromagnetic material consisting mainly of iron and a rare earth element;   a fluoride compound or an oxyfluoride compound formed inside crystal grains or in a portion of grain boundary area of the ferromagnetic material;   at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements and carbon contained in the fluoride compound or the oxyfluoride compound; and   a continuously extending layer formed by the fluoride compound or the oxyfluoride, the continuously extending layer extending in a grain boundary at any locus of the ferromagnetic material without being connected to an outermost surface of the ferromagnetic material, wherein   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates along the continuously extending layer and along a grain boundary of a matrix of the ferromagnetic material, and   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates within grains of the fluoride compound or the oxyfluoride compound having a cubic crystal structure in an increasing concentration from a center of the grain toward outer side thereof.   
     
     
         7 . A rotating machine equipped with a sintered magnet, the sintered magnet comprising:
 a ferromagnetic material consisting mainly of iron, a rare earth element, and a half-metallic element;   a fluoride compound or an oxyfluoride compound formed inside crystal grains or in a portion of grain boundary area of the ferromagnetic material;   at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements and carbon or nitrogen contained in the fluoride compound or the oxyfluoride compound; and   a continuously extending layer formed by the fluoride compound or the oxyfluoride, the continuously extending layer extending from a surface of the ferromagnetic material through the inside of the ferromagnetic material to an opposite side surface of the ferromagnetic material, wherein   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates in an outer peripheral portion within the grain along the continuously extending layer and along the grain boundary of the ferromagnetic material, and grains of the fluoride compound or the oxyfluoride compound are formed,   there are present in a portion of the grains of the fluoride compound or the oxyfluoride compound a gradient of concentration in which the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, half-metallic elements, and rare earth elements is in an increasing concentration from a center of the grain toward an outer side of the grain in a portion of the grains of the fluoride compound or the oxyfluoride compound, and an average concentration of at least one element selected from the group consisting of fluorine, rare earth element, or carbon measured over an area not smaller than 100 μm 2  is such that a ratio of a value measured in an area within a depth of 100 μm from an outermost surface of the ferromagnetic material excluding a protective layer to a value measured in an area including a central part at a distance of not smaller than 100 μm from the outermost surface is 1±0.5.   
     
     
         8 . A rotating machine equipped with a sintered magnet, the sintered magnet comprising:
 a ferromagnetic material consisting mainly of iron, a rare earth element, and a half-metallic element;   a fluoride compound or an oxyfluoride compound formed inside crystal grains or in a portion of grain boundary area of the ferromagnetic material;   at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements and carbon or nitrogen contained in the fluoride compound or the oxyfluoride compound; and   a continuously extending layer formed by the fluoride compound or the oxyfluoride, the continuously extending layer extending in a grain boundary at any locus of the ferromagnetic material so as to surround one or more crystal grains without being connected to an outermost surface of the ferromagnetic material, wherein   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates along the continuously extending layer and along a grain boundary of a matrix of the ferromagnetic material, and   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates within grains of the fluoride compound or the oxyfluoride compound having a structure of a cubic, hexagonal, or tetragonal crystal in an increasing concentration from a center of the grain toward outside thereof.   
     
     
         9 . A rotating machine equipped with a sintered magnet, the sintered magnet comprising:
 a ferromagnetic material consisting mainly of iron, a rare earth element, and a half-metallic element;   a fluoride compound or an oxyfluoride compound formed inside crystal grains or in a portion of grain boundary area of the ferromagnetic material;   at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements and carbon or nitrogen contained in the fluoride compound or the oxyfluoride compound; and   a continuously extending layer formed by the fluoride compound or the oxyfluoride, the continuously extending layer extending in a grain boundary at any locus of the ferromagnetic material so as to surround one or more crystal grains without being connected to an outermost surface of the ferromagnetic material, wherein   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates along the continuously extending layer and along a grain boundary of a matrix of the ferromagnetic material in a concentration higher than that in a center of the grain boundary, and   the at least one element selected from the group consisting of alkalis, alkaline earth elements, metal elements, and rare earth elements segregates within grains of the fluoride compound or the oxyfluoride compound having a symmetry of a cubic, hexagonal, or tetragonal crystal in an increasing concentration from a center of the grain toward outside thereof.   
     
     
         10 . A method for producing a sintered magnet for producing the sintered magnet of the rotating machine according to  claim 1 , the method comprising:
 molding the ferromagnetic material to form a preform of a magnet; and   impregnating or coating the preform with the fluoride compound or the oxyfluoride compound dissolved in a solution having optical transparency or low viscosity and then sintering the impregnated or coated preform.   
     
     
         11 . A method for producing a sintered magnet for producing the sintered magnet of the rotating machine according to  claim 2 , the method comprising:
 molding the ferromagnetic material to form a preform of a magnet; and   impregnating or coating the preform with the fluoride compound or the oxyfluoride compound dissolved in a solution having optical transparency or low viscosity and then sintering the impregnated or coated preform.   
     
     
         12 . A method for producing a sintered magnet for producing the sintered magnet of the rotating machine according to  claim 3 , the method comprising:
 molding the ferromagnetic material to form a preform of a magnet; and   impregnating or coating the preform with the fluoride compound or the oxyfluoride compound dissolved in a solution having optical transparency or low viscosity and then sintering the impregnated or coated preform.   
     
     
         13 . A method for producing a sintered magnet for producing the sintered magnet of the rotating machine according to  claim 4 , the method comprising:
 molding the ferromagnetic material to form a preform of a magnet; and   impregnating or coating the preform with the fluoride compound or the oxyfluoride compound dissolved in a solution having optical transparency or low viscosity and then sintering the impregnated or coated preform.   
     
     
         14 . A method for producing a sintered magnet for producing the sintered magnet of the rotating machine according to  claim 5 , the method comprising:
 molding the ferromagnetic material to form a preform of a magnet; and   impregnating or coating the preform with the fluoride compound or the oxyfluoride compound dissolved in a solution having optical transparency or low viscosity and then sintering the impregnated or coated preform.   
     
     
         15 . A method for producing a sintered magnet for producing the sintered magnet of the rotating machine according to  claim 6 , the method comprising:
 molding the ferromagnetic material to form a preform of a magnet; and   impregnating or coating the preform with the fluoride compound or the oxyfluoride compound dissolved in a solution having optical transparency or low viscosity and then sintering the impregnated or coated preform.