Permanent magnet with high max. energy prod. and corrosion resistance - comprises transition metal, rare earth metal, nitrogen and boron

摘要

Permanent magnet contains 60-68 (wt.%) transition element(s) (I), 30-38% rare earth element(s) (II) 0.1-1.5% N and 0.8-1.5%.B. {ref/ (I) is Fe, opt. mixed with Co (max. 15% of the total) to increase the Curie temp.; and (II) is Nd, opt. mixed with Dy (max. 5% of the total) to increase the intrinsic coercivity and Ce (max. 10% of the total). The N content is 1.2-1.3% and the magnet may also contain Al to increase the intrinsic coercivity. The magnetic is produced by (a) melting (I), (II) and B in a predetermined ratio; (b) cooling the molten soln. to form a tlump of alloy; (c) pulversing the alloy to a dia. of 2-6 micorns; (d) consolidating the powder under N2 in a metal mould in a magnetic field to form a green moulding; (e) sintering this in a N2 atmos. for at least 1 h at 1000-1100 deg.C and constant N2 partial pressure (pref. 0.01 torr); and opt. (f) heat treatment, pref. at 500-900 deg.C. USE/ADVANTAGE - The magnet has a high max. energy prod. and good corrosion resistance. It can be produced in a N2 atmos. which makes the mfg. cost more acceptable than with inert gas and is safer than operating under H2 at high temp.