Rare earth magnet and a method for manufacturing compactable powder for the rare earth magnet without jet milling
The present invention discloses manufacturing methods of a powder for compacting rare earth magnet powder and rare earth magnet that omit jet milling process, which comprises the steps as follows: 1) casting: casting the molten alloy of rare earth magnet raw material by strip casting method to obtain a quenched alloy with average thickness in a range of 0.2˜0.4 mm; 2) hydrogen decrepitation: decrepitating the quenched alloy and a plurality of rigid balls into a rotating hydrogen decrepitation container simultaneously, the quenched alloy is crushed under a hydrogen pressure between 0.01˜1 MPa, cooling the alloy and the balls, then screening the mixture to remove the rigid balls and obtain the powder. As the jet milling process is omitted, the oxygenation during the process of the jet milling may be avoided, therefore the process may be non-oxide, and the mass production of magnet with super high property may be possible.
1. A method of manufacturing a compactable powder for a rare earth magnet without jet milling, the rare earth magnet comprising a R 2 T 14 B main phase, where R is at least one rare earth element including yttrium, and T is at least one transition metal element including Fe, wherein the method comprises the steps of:
casting a molten alloy of a rare earth magnet raw material by strip casting and cooling to obtain a quenched alloy with an average thickness ranging from 0.2˜0.4 mm;
putting the quenched alloy and a plurality of rigid balls into a rotatable hydrogen decrepitation container;
hydrogen decrepitating and simultaneously ball milling by rotating the rotatable hydrogen decrepitation container to crush the quenched alloy under a hydrogen pressure ranging between 0.01 to 1 MPa and to produce a mixture;
dehydrogenating and simultaneously ball milling by rotating the rotatable hydrogen decrepitation container to crush the mixture and produce the compactable powder;
screening the compactable powder from the plurality of rigid balls to remove the plurality of rigid balls; and
passing the compactable powder through a 300˜1500 mesh screen without further pulverization of the compactable powder after dehydrogenating and simultaneously ball milling,
wherein the plurality of rigid balls does not break during rotating the rotatable hydrogen decrepitation container.
2. The method according to claim 1 , wherein more than 95 weight % of the quenched alloy has a thickness ranging from 0.1˜0.7 mm.
3. The method according to claim 1 , wherein the rotatable hydrogen decrepitation container has a rotation rate that ranges from 30 rpm˜100 rpm.
4. The method according to claim 1 ,
wherein cooling to obtain the quenched alloy is accomplished at a cooling rate ranging between 10 2 ° C./s˜10 4 ° C./s and an average cooling rate ranging between 1*10 3 ° C./s˜8*10 3 ° C./s,
wherein hydrogen decrepitating takes place for a hydrogen decrepitation period ranging from 1˜24 hours, and
wherein dehydrogenating the compactable powder takes place for a dehydrogenation period ranging from 0.5˜10 hours.
5. The method according to claim 1 , wherein the plurality of rigid balls are rigid balls selected from the group consisting of steel balls, metal Mo balls, metal W balls, stainless steel balls, tungsten carbide balls, aluminum oxide balls, zirconium oxide balls or silicon carbide balls, and have a ball size ranging from 0.5 mm˜60 mm.
6. The method according to claim 1 , wherein the method further comprises, prior to hydrogen decrepitating, preheating the quenched alloy to a temperature ranging from 150° C.˜350° C.
7. The method according to claim 1 , wherein the quenched alloy is expressed, in atomic percent, as:
R e T f A g J h G i D k ,
where R is Nd or comprises Nd and at least one of La, Ce, Pr, Sm, Gd, Dy, Tb, Ho, Er, Eu, Tm, Lu or Y;
where T is Fe or comprises Fe and at least one of Ru, Co or Ni;
where A is B or comprises B and at least one of C or P;
where J is at least one of Cu, Mn, Si or Cr;
where G is at least one of Al, Ga, Ag, Bi or Sn;
where D is at least one of Zr, Hf, V, Mo, W, Ti or Nb; and
where subscripts e, f, g, h, i and k are configured as:
12≤e≤16,
5≤g≤9,
0.05≤h≤1,
0.2≤i≤2.0,
k is 0≤k≤4, and
f=100-e-g-h-i-k.
8. The method according to claim 1 , wherein the rare earth magnet raw material has a proportion of Co that is below 1 at %.
9. The method of claim 1 , wherein the method further comprises, prior to hydrogen decrepitating, preheating the quenched alloy to a temperature ranging from 150° C.˜250° C.
10. A method of manufacturing a rare earth magnet without jet milling, the rare earth magnet comprising a R 2 T 14 B main phase, where R is at least one rare earth element including yttrium, and T is at least one transition metal element including Fe, wherein the method comprises the steps of:
casting a molten alloy of a rare earth magnet raw material by strip casting to obtain a quenched alloy having an average thickness ranging from 0.2˜0.4 mm;
putting the quenched alloy and a plurality of rigid balls into a rotatable hydrogen decrepitation container;
rotating the rotatable hydrogen decrepitation container to hydrogen decrepitate and simultaneously ball milling to crush the quenched alloy under a hydrogen pressure ranging between 0.01 to 1 MPa and produce a mixture;
dehydrogenating and simultaneously ball milling by rotating the rotatable hydrogen decrepitation container to crush the mixture and produce compactable powder;
screening the compactable powder from the plurality of rigid balls to remove the plurality of rigid balls;
compacting, after screening and without further pulverization of the compactable powder after dehydrogenating and simultaneously ball milling, the compactable powder in a two-part compacting method comprising magnetic field compacting and isostatic pressing compacting to provide a green compact; and
sintering the green compact to provide the rare earth magnet, wherein the rare earth magnet is a permanent magnet,
wherein the plurality of rigid balls does not break during rotating the rotatable hydrogen decrepitation container.
11. The method of claim 10 , wherein the method further comprises adding an organic additive to the compactable powder prior to compacting the compactable powder.
12. The method of claim 11 , wherein a weight ratio of the organic additive to the compactable powder ranges from 0.01:100˜1.5:100.
13. The method of claim 11 , wherein the organic additive is methyl caprylate.
14. The method of claim 10 , wherein the two-part compacting method comprises demagnetizing the compactable powder between magnetic field compacting and isostatic pressing compacting.
15. The method of claim 14 , wherein the two-part compacting method comprises sealing, so as to not expose to air, the compactable powder between magnetic field compacting and isostatic pressing compacting.
16. The method of claim 10 , wherein the two-part compacting method comprises sealing, so as to not expose to air, the compactable powder between magnetic field compacting and isostatic pressing compacting.
17. The method of claim 10 , wherein magnetic field compacting forms a cube in an orientation field of 2.1 T.
18. The method of claim 10 , wherein the method further comprises heating the rare earth magnet in an atmosphere of Ar gas after sintering the green compact.
19. The method of claim 10 , wherein an oxygen content of the rare earth magnet after the sintering is less than 1000 ppm.
20. The method of claim 10 , wherein an oxygen content of the rare earth magnet after the sintering is less than 450 ppm.