Rare earth - manufacturing method of transition metal-based alloy powder

摘要

PROBLEM TO BE SOLVED: To provide a rare-earth transition metal-based alloy powder in which the demagnetization curve squareness of the rare-earth transition metal-based alloy powder obtained by a reduction diffusion method is improved to enhance its permanent-magnet performance; and to provide a method for the production thereof.SOLUTION: The rare-earth transition metal-based alloy powder is produced by the method which includes: a first step of mixing a powder of a rare-earth metal oxide with a powder of a transition metal and/or a powder of an oxide thereof and at least one reducing agent selected from among particulate or powdery alkali metals, alkaline earth metals, and hydrides thereof and keeping the mixture at 850-1,200°C for 1-10 hours in an inert atmosphere to obtain a reaction mixture containing a rare-earth transition metal-based alloy; a second step of cooling the reaction mixture to 300°C or lower, feeding a hydrogen gas thereinto, and keeping the resultant mixture at a temperature of 700-900°C for 1-20 hours in an atmosphere of a hydrogen gas partial pressure of 20-40 kPa; a third step of heat-treating the obtained reaction mixture at 500-900°C for 10 minutes to 20 hours in vacuum or in an atmosphere of a hydrogen gas partial pressure of less than 10 kPa; a fourth step of cleaning the obtained heat-treated product with water to remove therefrom reaction products containing the reducing agent to recover the rare-earth transition metal-based alloy; and a fifth step of drying the cleaned rare-earth transition metal-based alloy in a non-oxidizing atmosphere of 150-400°C.