Methods to Lower the Production Costs of Magnets and Magnetic Materials

Abstract

Lower cost commercial grades of rare earth metals as terbium, dysprosium and holmium contain impurities with higher melting points than that of the desired alloy. The impurities would contaminate magnetostrictive rods and interfere with their desired properties. O. McMasters IOWA STATE UNIVERSITY RESEARCH FOUNDATION, INC. 14.1? has found a method for large scale commercial manufacture of grain-oriented rods. Semi-homogenized buttons, fingers or the like of the rare earth alloy can be charged to a crucible of relatively large capacity in relation to the individual increments, to form a homogeneous melt. The melt in the crucible is held long enough to permit particles of solid contaminants to collect at its upper surface. These operations are carried out under an inert atmosphere which may be subsequently used to create a pressure forcing the melt into upwardly-extending tubes having their lower ends immersed in the melt. Means are provided for inserting and removing the tubes from the melt. The lower ends of the tubes are positioned well below the upper surface of the melt where the solid impurities collect. The molten alloy rises in the mold tubes to the selected level for forming the rods.