PM-Wire Permanent Magnet Manufacturing Process for Domestically Sintered Neodymium Iron Boron Magnets for Weapons Platforms

There is a critical need for manufacturing capabilities of high-performance permanent magnets in the U.S. for defense applications. Several rare earth material mining ventures are under development in the U.S. and domestic extraction of raw materials for permanent magnets will become available in the coming years. However, currently there is very little production capability for NdFeB permanent magnets in the U.S.; the manufacturing process of sintered permanent magnets is very labor intensive and requires over 50 steps restricting cost effective production to countries with inexpensive labor. Once domestic supply of NdPr becomes available in the US, only an innovative manufacturing process for permanent magnets with a high level of automation can be viable and produce cost competitive magnets. AML developed a novel manufacturing process called PM-Wire™ allowing for fully automated cost-effective production of permanent magnets that will bring permanent magnet manufacturing back to the U.S. AML’s PM-Wire™ is a novel manufacturing process for permanent magnets based on a powder-in-tube process in which the permanent magnet powder is placed in a thin metal tube under a magnetic field for pre-alignment and creation a preferred direction of magnetization. The magnetic material is then compress through sizing of the tube until the cross-section area is reduced by 50% or more and the tube cross-section is changed to the desired shape. The PM-Wire™ magnet is then shaped, sintered/heat treated as needed and magnetized. Since sintering is performed at high temperature, typically over 1,000 C, a metal with a low melting point is selected for the jacket. As a result, the jacket material goes into a liquid state during sintering and either flows away from the permanent material or, if the viscosity and surface tension are too large, conforms to the permanent magnet material preventing voids and cracks from forming. The resulting permanent magnet is very close to the final useful shape and will require very little grinding, if any. The overall objective of this project is to demonstrate manufacturing and qualification of sintered NdFeB permanent magnets for a defense application as a first step leading eventually to large scale manufacturing.