Ferrite Magnetic Powder for Bond Magnet and Manufacturing Method of the Same, and Bond Magnet

Abstract

To provide ferrite magnetic powders for bond magnet capable of surely suppressing residual hexavalent chrome, being an environmental load substance, having no adverse influence on the magnetic characteristics, which is an obstacle in use, and without damaging productivity and at a low cost. The method includes the steps of obtaining sintered powders by sintering raw material powders; wet-pulverizing the sintered powders; wet-cleaning the sintered powders; and annealing the cleaned sintered powders, wherein in the step of the wet-pulverization and in the step of wet-cleaning, generation of the hexavalent chrome, being an environmental load substance, is suppressed by performing the pulverization and cleaning while maintaining pH of a dispersion solvent at 8.5 or less, at the time of pulverization and cleaning.

1 . Ferrite magnetic powders, which are the ferrite magnetic powders for bond magnet containing iron and an alkaline earth metal, subjected to wet cleaning and/or wet pulverizing process, said ferrite magnetic powders containing a Cr element of 100 ppm or more and 3000 ppm or less, with no hexavalent chrome detected therein. 
   
   
       2 . Ferrite magnetic powders, which are the ferrite magnetic powders for bond magnet containing iron and an alkaline earth metal, subjected to wet cleaning and/or wet pulverizing process, said ferrite magnetic powders containing a Cr element of 100 ppm or more and 3000 ppm or less, with content of a hexavalent chrome set at 1 ppm or less. 
   
   
       3 . The ferrite magnetic powders according to  claim 1 , wherein in magnetic characteristics of a compact prepared by adding 0.4 cc of polyester resin to 7 g of the ferrite magnetic powders, then filling this mixture into a mold of φ15 mm, and adding pressure of 8 MPa thereto, residual magnetic flux density is 173 OGauss or more and intrinsic coercive force iHc is 2270 Oe or more. 
   
   
       4 . A manufacturing method of ferrite magnetic powders for bond magnet, which is the manufacturing method of the ferrite magnetic powders for manufacturing the ferrite magnetic powders for bond magnet from raw material powders containing iron and an alkaline earth metal, comprising the steps of:
 obtaining sintered powders by sintering said raw material powders;   wet-cleaning said sintered powders; and   annealing the wet-cleaned sintered powders.   wherein in the step of wet-cleaning, cleaning is performed, with pH of a dispersion solvent used in cleaning set at 8.5 or less.   
   
   
       5 . A manufacturing method of ferrite magnetic powders for bond magnet, which is the manufacturing method of ferrite magnetic powders for manufacturing the ferrite magnetic powders for bond magnet from raw material powders containing iron and alkaline earth metal, comprising the steps of:
 obtaining sintered powders by sintering said raw material powders;   pulverizing said sintered powders;   wet-cleaning the pulverized sintered powders; and   annealing said wet-cleaned sintered powders,   wherein in the step of wet-cleaning, cleaning is performed, with pH of a dispersion solvent used in the cleaning set at 8.5 or less.   
   
   
       6 . A manufacturing method of ferrite magnetic powders for bond magnet, which is the manufacturing method of ferrite magnetic powders for manufacturing the ferrite magnetic powders for bond magnet from raw material powders containing iron and alkaline earth metal, comprising the steps of:
 obtaining sintered powders by sintering said raw material powders;   wet-pulverizing said sintered powders; and   annealing said wet-pulverized sintered powders,   wherein in the step of wet-pulverization, wet-pulverization is performed, with pH of a dispersion solvent used in the wet-pulverization set at 8.5 or less.   
   
   
       7 . The manufacturing method of the ferrite magnetic powders according to  claim 4 , wherein carbon and/or a compound having a boiling point of 200° C. or more with carbon as an indispensable element and one or more kinds of elements selected from H, O, N, Cl contained therein, is added to said sintered powders after the step of obtaining the sintered powders and before the step of annealing. 
   
   
       8 . The manufacturing method of ferrite magnetic powders for bond magnet according to  claim 4 , wherein bivalent Fe and/or a compound containing the bivalent Fe is added to said sintered powders, after the step of obtaining the sintered powders and before the step of annealing. 
   
   
       9 . The manufacturing method of ferrite magnetic powders for bond magnet according to  claim 4 , wherein reduction treatment is applied to the sintered powders subjected to wet-pulverization and/or wet cleaning in a gas atmosphere in a temperature range from 80° C. to 300° C., containing one or more gasses selected from H 2  gas, CO gas, NO gas, and HC (hydrocarbon) gas. 
   
   
       10 . A bond magnet, containing the ferrite magnetic powders for bond magnet according to  claim 1 . 
   
   
       11 . The ferrite magnetic powders according to  claim 2 , wherein in magnetic characteristics of a compact prepared by adding 0.4 cc of polyester resin to 7 g of the ferrite magnetic powders, then filling this mixture into a mold of φ15 mm, and adding pressure of 8 MPa thereto, residual magnetic flux density is 173 OGauss or more and intrinsic coercive force iHc is 22700 e or more. 
   
   
       12 . The manufacturing method of the ferrite magnetic powders according to  claim 5 , wherein carbon and/or a compound having a boiling point of 200° C. or more with carbon as an indispensable element and one or more kinds of elements selected from H, O, N, Cl contained therein, is added to said sintered powders after the step of obtaining the sintered powders and before the step of annealing. 
   
   
       13 . The manufacturing method of the ferrite magnetic powders according to  claim 6 , wherein carbon and/or a compound having a boiling point of 200° C. or more with carbon as an indispensable element and one or more kinds of elements selected from H, O, N, Cl contained therein, is added to said sintered powders after the step of obtaining the sintered powders and before the step of annealing. 
   
   
       14 . The manufacturing method of ferrite magnetic powders for bond magnet according to  5 , wherein bivalent Fe and/or a compound containing the bivalent Fe is added to said sintered powders, after the step of obtaining the sintered powders and before the step of annealing. 
   
   
       15 . The manufacturing method of ferrite magnetic powders for bond magnet according to  6 , wherein bivalent Fe and/or a compound containing the bivalent Fe is added to said sintered powders, after the step of obtaining the sintered powders and before the step of annealing. 
   
   
       16 . The manufacturing method of ferrite magnetic powders for bond magnet according to  claim 5 , wherein reduction treatment is applied to the sintered powders subjected to wet-pulverization and/or wet cleaning in a gas atmosphere in a temperature range from 80° C. to 300° C., containing one or more gasses selected from H 2  gas, CO gas, NO gas, and HC (hydrocarbon) gas. 
   
   
       17 . The manufacturing method of ferrite magnetic powders for bond magnet according to  claim 6 , wherein reduction treatment is applied to the sintered powders subjected to wet-pulverization and/or wet cleaning in a gas atmosphere in a temperature range from 80° C. to 300° C., containing one or more gasses selected from H 2  gas, CO gas, NO gas, and HC (hydrocarbon) gas. 
   
   
       18 . A bond magnet, containing the ferrite magnetic powders for bond magnet according to  claim 2 . 
   
   
       19 . A bond magnet, containing the ferrite magnetic powders for bond magnet according to  claim 3 . 
   
   
       20 . A bond magnet, containing the ferrite magnetic powders for bond magnet according to  11