A corrosion-resistant magnet from the tm - b - re - type and its production method

摘要

PURPOSE:To cause the title magnet to have both high magnetic characteristics and high corrosion resistance by mixing and pressing a powder mainly composed of an intermetallic compound having a specific RE2TM14B composition and one or more kinds of powder having, as a main phase, RE-TM interfamily compound or RE-TM-B intermetallic compound lower in the melting point than the first powder and thereafter by sintering the obtained product. CONSTITUTION:A mixed powder of a permanent magnet alloy, which consists of RE not less than 10% and not more than 25% including one or two sorts or materials selected from Y, Sc and lanthanoids, B of not less then 2% and not more than 20% and the rest TM and its constitution is in the phase od RE2TM14B composition having Nd2Fe14B structure, and a powder mainly composed of RE-TM intermetallic compound phase or RE-TM eutectic structure and/or RE-TM-B intermetallic compound phase lower in the melting point than the first phase is subjected to compression molding and sintered thereafter. For further improvement of corrosion resistance, it is effective that a grain boundary phase is electrochemically nobler than a main phase. Therefore, it is preferable to make the ratio of Ni and/or Co in TM in the RE-TM and RE-TM-B low melting point phase higher than that in the RE2TM14B phase.