Iron-based permanent magnets and their fabrication as well as iron-based permanent magnet alloy powders for permanent bonded magnets and iron-based bonded magnets

Abstract

With the invention of establishing fabrication methods for cheaply produced (Fe,Co)-Cr-B-R-type bonded magnets or (Fe,Co)-Cr-B-R-M-type bonded magnets containing few rare earth elements having a coercive force iHc above 5 kOe and a residual magnetic flux density Br above 5.5 kG matching the cost performance of hard ferrite magnets, we have obtained iron-based permanent magnets consisting of microcrystal clusters where the average crystal size of each component phase is in the range 1 nm ~30 nm and where both a soft magnetic phase consisting of a ferromagnetic alloy whose main components are alpha-Fe and a ferromagnetic alloy having iron, and a hard magnetic phase having a Nd2Fe14B-type crystal structure coexist within the same powder particles, by melt-quenching of a (Fe,Co)-Cr-B-R(Pr,Nd)-type molten alloy or a (Fe,Co)-Cr-B-R-M (M=Al,Si,S,Ni, Cu,Zn,Ga,Ag,Pt,Au,Pb)-type molten alloy of a particular composition containing few rare earth elements, to obtain an essentially amorphous structure or a structure both amorphous and with small amounts of fine crystals, and by applying a crystallization heat treatment under specific conditions. By grinding this iron-based permanent magnet to an average powder particle size of 3 mum~500 mum and combining the resultant iron-based permanent magnet alloy powder with a resin, we can obtain an iron-based bonded magnetic with good thermal and magnetic properties and with the magnetic characteristics iHc>=5 kOe, Br>=5.5 kG and (BH)max>=6 MGOe.

What is claimed is:  
     
       1. An iron-based permanent magnet consisting of fine crystal aggregates consisting of mutually distributed magnetically soft and hard magnetic phases, wherein the permanent magnet has a compositional formula represented by Fe 100-x-y-z-a Cr x B y R z Co a  (where R is Pr or Nd or mixtures thereof), wherein symbols x, y, z, and a satisfy the following values: 
       0.01≦x≦7 at %  
       15<y≦30 at %  
       3≦z≦6 at %  
       0.01≦a≦30 at %,  
       and wherein the soft magnetic phase, which consists of α-iron and a ferromagnetic phase containing iron as a main component, and the hard magnetic phase, which has a Nd 2 Fe 14 B crystal structure, coexist in the permanent magnet, provided that the hard magnetic phase having a Nd 2 Fe 14 B crystal structure is not a primary phase of said iron-base permanent magnet, the constituent phases of the permanent magnet having mean crystal sizes within the range of 1 nm to 30 nm. 
     
     
       2. An iron-base permanent magnet consisting of fine crystal aggregates which consist of mutually distributed magnetically soft and hard magnetic phases, the permanent magnet having a compositional formula represented by Fe 100-x-y-z-a-b Cr x B y R z Co a M b  (where R is Pr or Nd or mixtures thereof, M is one or more selected from the group consisting of Al, Si, S, Ni, Cu, Zn, Ga, Ag, Pt, Au and Pb), wherein symbols x, y, z, a, and b satisfy the following values: 
       0.01≦x≦7 at %  
       15<y≦30 at %  
       3≦z≦6 at %  
       0.01≦a≦30 at %,  
       0.01≦b≦10 at %,  
       and wherein the soft magnetic phase, which consists of α-iron and a ferromagnetic phase containing iron as a main component, and the hard magnetic phase, which has a Nd 2 Fe 14 B crystal structure, coexist in the permanent magnet, provided that the hard magnetic phase having a Nd 2 Fe 14 B crystal structure is not a primary phase of said iron-base permanent magnet, the constituent phases of the permanent magnet having mean crystal sizes within the range of 1 nm to 30 nm. 
     
     
       3. An iron-based permanent magnet consisting of fine crystal aggregates, the magnetic powder having a compositional formula represented by Fe 100-x-y-z-a Cr x B y R z Co a  (where R is Pr or Nd or mixtures thereof), wherein symbols x, y, z, and a satisfy the following values: 
       0.01≦x≦7 at %  
       15<y≦30 at %  
       3≦z≦6 at %  
       0.01≦a≦30 at %,  
       in which a soft magnetic phase, which consists of α-iron and a ferromagnetic alloy having iron as a main component, and the hard magnetic phase, which has a Nd 2 Fe 14 B crystal structure, coexist in each powder particle, provided that the hard magnetic phase having a Nd 2 Fe 14 B crystal structure is not a primary phase of said iron-base permanent magnet powder, the constituent phases of the powder particles having mean crystal sizes within the range of 1 nm to 30 nm and the powder particles having mean particle sizes of 3 μto 500 μm and magnetic characteristics of iHc>5 kOe, Br>7 kG, (BH)max≧8 MGOe. 
     
     
       4. An iron-base permanent magnet powder for a bonded magnet consisting of fine crystal aggregates, said magnet powder having a compositional formula represented by Fe 100-x-y-z-a-b Cr x B y R z Co a M b  (where R is Pr or Nd or mixtures thereof, M is one or more element selected from the group consisting of Al, Si, S, Ni, Cu, Zn, Ga, Ag, Pt, Au and Pb), with symbols x, y, z, a, and b satisfy the following values: 
       0.01≦x≦7 at %  
       15<y≦30 at %  
       3≦z≦6 at %  
       0.01≦a≦30 at %,  
       0.01≦b≦10 at %,  
       in which a soft magnetic phase, which consists of α-iron and a ferromagnetic alloy having iron as a main component, and the hard magnetic phase, which has a Nd 2 Fe 14 B crystal structure, coexist in each powder particle, provided that the hard magnetic phase having a Nd 2 Fe 14 B crystal structure is not a primary phase of said magnet powder, the constituent phases of the powder particles having mean crystal sizes within the range of 1 nm to 30 nm, and the powder particles having mean particle size of 3 μm to 500 μm and magnetic characteristics of iHc>5 kOe, Br>7.2 kG, (BH)max≧8.4 MGOe. 
     
     
       5. An iron-base bonded magnet obtained by combining resin and iron-base permanent magnet powder consisting of fine crystal aggregates, said magnet powder having a compositional formula represented by Fe 100-x-y-z-a Cr x B y R z Co a  (where R is Pr or Nd or mixtures thereof), with symbols x, y, z, and a satisfy the following values: 
       0.01≦x≦7 at %  
       15<y≦30 at %  
       3≦z≦6 at %  
       0.01≦a≦30 at %,  
       in which a soft magnetic phase, which consists of α-iron and a ferromagnetic alloy having iron as a main component, and a hard magnetic phase, which has a Nd 2 Fe 14 B crystal structure, coexist in each powder particle, provided that the hard magnetic phase having a Nd 2 Fe 14 B crystal structure is not a primary phase of said iron-base permanent magnet powder, the constituent phases of the powder particles having mean crystal sizes within the range of 1 nm to 30 nm, and the powder particles having a mean particle size of 3 μm to 500 μm and magnetic characteristics of iHc≧5 kOe, Br≧5.5 kG, (BH)max≧6 MGOe. 
     
     
       6. An iron-base bonded magnet obtained by combining resin and iron-base permanent magnet powder, consisting of fine crystal aggregates, said magnet powder having a compositional formula represented by Fe 100-x-y-z-a-b Cr x B y R z Co a M b  (where R is Pr or Nd or mixtures thereof, and M is one or more elements selected from the group consisting of Al, Si, S, Ni, Cu, Zn, Ga, Ag, Pt, Au, Pb), with symbols x, y, z, a, and b satisfy the following values: 
       0.01≦x≦7 at %  
       15<y≦30 at %  
       3≦z≦6 at %  
       0.01≦a≦30 at %  
       0.01≦b≦10 at %,  
       wherein a soft magnetic phase, which consists of a ferromagnetic alloy having α-iron and iron as main components, and a hard magnetic phase, which has a Nd 2 Fe 14 B crystal structure, coexist in each powder particle, provided that the hard magnetic phase having a Nd 2 Fe 14 B crystal structure is not a primary phase of said iron-base permanent magnet powder, the constituent phases of the powder particles having mean crystal sizes within the range of 1 nm to 30 nm and the powder particles having magnetic mean particle size of 3 μm to 500 μm magnetic characteristics of iHc≧5 kOe, Br≧5.5 kG, (BH)max≧6 MGOe. 
     
     
       7. The magnet as defined in  claim 1 , wherein the soft magnetic phase is a main phase of the magnet. 
     
     
       8. The magnet as defined in  claim 2 , wherein the soft magnetic phase is a main phase of the magnet. 
     
     
       9. The magnet powder as defined in  claim 3 , wherein the soft magnetic phase is a main phase of the magnet powder. 
     
     
       10. The magnet powder as defined in  claim 4 , wherein the soft magnetic phase is a main phase of the magnet powder. 
     
     
       11. The magnet powder as defined in  claim 5 , wherein the soft magnetic phase is a main phase of the magnet powder. 
     
     
       12. The magnet powder as defined in  claim 6 , wherein the soft magnetic phase is a main phase of the magnet powder. 
     
     
       13. The magnet as defined in  claim 1 , wherein said soft and hard magnetic phases are obtained by heat treating a rapidly solidified composition of said compositional formula so that α-iron crystallizes in an increasing proportion of the soft magnetic phases as the amount of Cr in said compositional formula increases, and said mean crystal size does not exceed 30 nm. 
     
     
       14. The magnet as defined in  claim 2 , wherein said soft and hard magnetic phases are obtained by heat treating a rapidly solidified composition of said compositional formula so that α-iron crystallizes in an increasing proportion of the soft magnetic phases as the amount of Cr in said compositional formula increases, and said mean crystal size does not exceed 30 nm. 
     
     
       15. The magnet powder as defined in  claim 3 , wherein said soft and hard magnetic phases are obtained by heat treating a rapidly solidified composition of said compositional formula so that α-iron crystallizes in an increasing proportion of the soft magnetic phases as the amount of Cr in said compositional formula increases, and said mean crystal size does not exceed 30 nm. 
     
     
       16. The magnet powder as defined in  claim 4 , wherein said soft and hard magnetic phases are obtained by heat treating a rapidly solidified composition of said compositional formula so that α-iron crystallizes in an increasing proportion of the soft magnetic phases as the amount of Cr in said compositional formula increases, and said mean crystal size does not exceed 30 nm. 
     
     
       17. The magnet powder as defined in  claim 5 , wherein said soft and hard magnetic phases are obtained by heat treating a rapidly solidified composition of said compositional formula so that α-iron crystallizes in an increasing proportion of the soft magnetic phases as the amount of Cr in said compositional formula increases, and said mean crystal size does not exceed 30 nm. 
     
     
       18. The magnet as defined in  claim 6 , wherein said soft and hard magnetic phases are obtained by heat treating a rapidly solidified composition of said compositional formula so that the α-iron crystallizes in an increasing proportion of the soft magnetic phases as the amount of Cr in said compositional formula increases, and said mean crystal size does not exceed 30 nm. 
     
     
       19. The magnet as defined in  claim 1 , wherein the soft magnetic phase consists essentially of α-iron. 
     
     
       20. The magnet as defined in  claim 2 , wherein the soft magnetic phase consists essentially of α-iron. 
     
     
       21. The magnet powder as defined in  claim 3 , wherein the soft magnetic phase consists essentially of α-iron. 
     
     
       22. The magnet powder as defined in  claim 4 , wherein the soft magnetic phase consists essentially of α-iron. 
     
     
       23. The magnet powder as defined in  claim 5 , wherein the soft magnetic phase consists essentially of α-iron. 
     
     
       24. The magnet powder as defined in  claim 6 , wherein the soft magnetic phase consists essentially of α-iron. 
     
     
       25. An iron-base permanent magnet powder having a compositional formula represented by Fe 100-x-y-z-a Cr x B y R z Co a  (where R is Pr or Nd or mixtures thereof), with symbols x, y, z, and a satisfy the following values: 
       0.01≦x≦3 at %  
       15<y≦20 at %  
       5≦z≦5.5 at %  
       1≦a≦10 at %,  
       and wherein a soft magnetic phase, which consists of α-iron and a ferromagnetic phase containing iron as a main component, and a hard magnetic phase, which has a Nd 2 Fe 14 B crystal structure, coexist in each powder particle, provided that the hard magnetic phase having a Nd 2 Fe 14 B crystal structure is not a primary phase of said iron-base permanent magnet powder, the constituent phases having mean crystal sizes within the range of 1 nm to 30 nm, and the powder particles magnetic characteristics of 5≦iHc≦6.5 kOe, Br>10 kG, (BH)max>12 MGOe. 
     
     
       26. An iron-base permanent magnet having a compositional formula represented by Fe 100-x-y-z-a-b Cr x B y R z Co a  (where R is Pr or Nd or mixtures thereof), wherein symbols x, y, z, and a satisfy the following values: 
       3<x≦7 at %  
       15<y≦20 at %  
       4≦z≦5.5 at %  
       1≦b≦10 at %,  
       and wherein a soft magnetic phase, which consists of α-iron and a ferromagnetic phase containing iron as a main component, and a hard magnetic phase, which has a Nd 2 Fe 14 B crystal structure, coexist in the permanent magnet, provided that the hard magnetic phase having a Nd 2 Fe 14 B crystal structure is not a primary phase of said iron-base permanent magnet, the constituent phases of the permanent magnet having mean crystal sizes within the range of 1 nm to 30 nm, and the permanent magnet having magnetic characteristics of iHc>6.5 kOe, 8≦Br≦10 kG, 10≦(BH)max≧12 MGOe. 
     
     
       27. An iron-base permanent magnet having a compositional formula represented by Fe 100-x-y-z-a-b Cr x B y R z Co a M b  (where R is Pr or Nd or mixtures thereof, and M is one or more elements selected from the group consisting of Al, Si, S, Ni, Cu, Zn, Ga, Ag, Pt, Au, and Pb), with symbols x, y, z, a, and b satisfy the following values: 
       0.01≦x≦3 at %  
       15<y≦20 at %  
       3≦z≦6 at %  
       1≦a≦10 at %  
       0.5≦b≦3 at %,  
       and wherein a soft magnetic phase, which consist of α-iron and a ferromagnetic phase containing iron as main component, and a hard magnetic phase, which has a Nd 2 Fe 14 B crystal structure, coexist in the permanent magnet, provided that the hard magnetic phase having a Nd 2 Fe 14 B crystal structure is not a primary phase of said iron-base permanent magnet, the constituent phases of the permanent magnet having mean crystal sizes within the range of 1 nm to 30 nm, and the permanent magnet having magnetic characteristics of 5≦iHc≦6.5 kOe, Br>10.2 kG, (BH)max>12.5 MGOe. 
     
     
       28. An iron-base permanent magnet having a compositional formula represented by Fe 100-x-y-z-a-b Cr x B y R z Co a M b  (where R is Pr or Nd or mixtures thereof, and M is one or more elements selected from the group consisting of Al, Si, S, Ni, Cu, Zn, Ga, Ag, Pt, Au, and Pb), with symbols x, y, z, a, and b satisfy the following values: 
       3<x≦7 at %  
       15<y≦20 at %  
       4≦z≦5.5 at %  
       1≦a≦10 at %  
       0.5≦b≦3 at %,  
       and where a soft magnetic phase, which consist of α-iron and a ferromagnetic phase containing iron as a main component, and a hard magnetic phase, which has a Nd 2 Fe 14 B crystal structure, coexist in the permanent magnet, provided that the hard magnetic phase having a Nd 2 Fe 14 B crystal structure is not a primary phase of said iron-base permanent magnet, the constituent phases of the permanent magnet having mean crystal sizes within the range of 1 nm to 30 nm and the permanent magnet having magnetic characteristics of iHc<6.5 kOe, 8.2≦Br≦10.2 kG, 10.5≦(BH)max≦12.5 MGOe.  
     
     
       29. The magnet as defined in  claim 25 , wherein said soft and hard magnetic phases are obtained by heat treating a rapidly solidified composition of said compositional formula so that α-iron crystallizes in an increasing proportion of the soft magnetic phases as the amount of Cr in said compositional formula increases, and said mean crystal size does not exceed 30 nm. 
     
     
       30. The magnet as defined in  claim 26 , wherein said soft and hard magnetic phases are obtained by heat treating a rapidly solidified composition of said compositional formula so that α-iron crystallizes in an increasing proportion of the soft magnetic phases as the amount of Cr in said compositional formula increases, and said mean crystal size does not exceed 30 nm. 
     
     
       31. The magnet as defined in  claim 27 , wherein said soft and hard magnetic phases are obtained by heat treating a rapidly solidified composition of said compositional formula so that α-iron crystallizes in an increasing proportion of the soft magnetic phases as the amount of Cr in said compositional formula increases, and said mean crystal size does not exceed 30 nm. 
     
     
       32. The magnet as defined in  claim 28 , wherein said soft and hard magnetic phases are obtained by heat treating a rapidly solidified composition of said compositional formula so that α-iron crystallizes in an increasing proportion of the soft magnetic phases as the amount of Cr in said compositional formula increases, and said mean crystal size does not exceed 30 nm.