Method for producing sintered Nd-Fe-B magnetic body containing no heavy rare earth element

摘要

The present invention relates to sintered Nd-Fe-B magnets, which are free of any heavy rare earth elements. The present invention further relates to corresponding manufacturing process thereof. The process comprises the steps of: a) providing an alloy sheet made of a Nd-Fe-B magnet composition, wherein Pr and Nd are present in a combined amount of 31 wt.% ‰¤ Pr and Nd ‰¤ 34wt.%; B is present in an amount of 0.8 wt.% ‰¤ B ‰¤ 1.2 wt%; Al is present in an amount of 0.4 wt.% ‰¤ Al ‰¤ 0.8 wt.%; Co is present in an amount of 0.6 wt.% ‰¤ Co ‰¤ 1.2 wt.%; Cu is present in an amount of 0.2 wt.% ‰¤ Cu ‰¤ 0.5 wt.%; Ga is present in an amount of 0.1 wt.% ‰¤ Ga ‰¤ 0.4 wt.%; and wherein the balance element is Fe; b) the alloy sheet is broken into alloy pieces by a decrepitation process; c) an amount of 0.05 to 0.5 wt.% lubricant is added to the alloy powder and then the mixture is milled by a jet mill process until an average particle size D50 of the resulting alloy powder ranges from 2.0 µm to 3.0 µm; d) another amount of 0.03 to 0.2 wt.% lubricant is added to the alloy powder after milling and mixed, then the alloy powder is compressed into compacts while applying an orienting magnetic field of 2.0 to 2.5T; and e) the compacts are sintered in a vacuum furnace, wherein a pressure within the furnace during the sintering step is equal to or less than 5x10 -2 Pa.