Rare earth permanent magnet material and manufacturing method thereof
The present invention provides a rare earth permanent magnet material and manufacturing method thereof. The manufacturing method of the present invention comprises a multi-arc ion plating step and a infiltrating step, wherein multi-arc ion plating process is adopted to deposit a metal containing a heavy rare earth element on a surface of a sintered neodymium-iron-boron magnet which has a thickness of 10 mm or less in at least one direction; and then heat treatment is performed on the sintered neodymium-iron-boron after deposition. The sum of an intrinsic coercive force (H cj , in unit of kOe) and a maximum magnetic energy product ((BH) max , in unit of MGOe) of the permanent magnet material of the present invention is 66.8 or more. Moreover, the manufacturing method of the present invention has high production efficiency and does not increase harmful substances, and the price of devices is relatively low.
1. A method for manufacturing a rare earth permanent magnet material, comprising steps as follows:
S1) magnet manufacturing step:
S1-1) smelting step: formulating raw materials consisting of the following ingredients with weight percentages: 27.4% of Nd, 4.5% of Dy, 0.97% of B, 2% of Co, 0.2% of Cu, 0.08% of Zr, 0.2% of Ga, 0.3% of Al and the balance of Fe; putting the raw materials in a vacuum rapid-hardening furnace to smelt them and manufacture an alloy sheet with an average thickness of 0.3 mm;
S1-2) powdering step: subjecting the alloy sheet obtained from the smelting step S1-1) to hydrogen absorption and dehydrogenation in a hydrogen decrepitation furnace to make coarse magnetic powder of about 300 μm; milling the coarse magnetic powder by jet milling with nitrogen as media into fine magnetic powder with an average particle size D50 of 3.8 μm;
S1-3) shaping step: applying an alignment magnetic field strength of 1.8T to shape the fine magnetic powder obtained from the powdering step S1-2) in a moulding press under protection of nitrogen to form a green body with a density of 4.3 g/cm3;
S1-4) sintering step: putting the green body obtained from the shaping step S1-3) in a vacuum sintering furnace with an absolute vacuum degree above 0.1 Pa, and sintering it at a high temperature of 1055° C. for 5 hours, to obtain a sintered neodymium-iron-boron magnet with a density of 7.63 g/cm3 and a size of 50 mm×40 mm×30 mm; and
S1-5) cutting step: cutting the sintered neodymium-iron-boron magnet obtained from the sintering step S1-4) into magnets with a size of 38 mm×23.5 mm×2.2 mm;
S2) multi-arc ion plating step: fixing an alloy block material of Tb and Al as a cathode material on a multi-arc ion discharging device, wherein the weight percentage of Tb in the alloy block material is 80%; placing the magnets obtained from the cutting process S1-5) in a processing chamber; evacuating the processing chamber to an absolute vacuum degree of 0.0005 Pa; applying a voltage to the multi-arc ion discharging device for 5 minutes to perform discharging, leading to evaporation and ionization of the cathode material, so that the alloy block material forms smoke-like microparticles during discharging; depositing the smoke-like microparticles on a surface of the magnets;
S3) infiltrating step: heat treating the magnets at 900° C. for 5 hours simultaneously with the multi-arc ion plating step S2); and
S4) aging treatment step: in a condition of an absolute vacuum degree above 0.01 Pa, performing aging treatment on the magnets obtained from the infiltrating step S3) at 510° C. for 3 hours to obtain the rare earth permanent magnet material.