Composite iron material

Claim 1

A mass of ferromagnetic particles in the size range of about 5 microns to about 400 microns for molding into stable, high strength, magnetic cores useful in thermally and chemically hostile environments, said particles each comprising an iron core and a single insulating material deposited directly onto and substantially continuously over, the entire surface of each said core so as to completely encapsulate said core in an electrically insulating outer shell of said material, said material being selected from the group consisting of amorphous thermoplastic polyetherimides, polyethersulfones and polyamideimides having heat distortion temperatures of at least about 200° C.

Claim 16

A method for making a magnetic core for an electromagnetic device comprising the steps of: spray-coating a mass of airborne ferromagnetic particles in the size range of about 5 microns to about 400 microns with an amorphous thermoplastic selected from the group consisting of polyetherimides, polyethersulfones and polyamideimides having a heat distortion temperature of at least about 200° C. to provide a mass of free-flowing thermoplastic-coated particles; conveying said free-flowing particles via a suitable conveyor into a heated die while substantially uniformly heating said particles in said conveyor enroute to the die to a temperature below, but within about 110° C. of, the softening temperature of said thermoplastic without losing the free-flowability of said particles; and applying at least about 20 tons per square inch pressure to said particles in said die or shape the core and coalesce the thermoplastic into a substantially continuous binder matrix for the ferromagnetic particles.

Claim 17

A method for making a magnetic core for an electromagnetic device comprising the steps of: spray-coating a mass of airborne ferromagnetic particles in the size range of about 5 microns to about 400 microns with an amorphous thermoplastic selected from the group consisting of polyetherimides, polyethersulfones and polyamideimides having a heat distortion temperature of at least about 200° C. to provide a mass of free-flowing thermoplastic-coated particles; conveying said free-flowing particles via a suitable conveyor into a heated die while substantially uniformly heating said particles in said conveyor enroute to the die to a temperature below, but within about 110° C. of, the softening temperature of said thermoplastic without losing the free-flowability of said particles; and applying at least about 20 tons per square inch pressure to said particles in said die or shape the core and coalesce the thermoplastic into a substantially continuous binder matrix for the ferromagnetic particles.

Claim 18

A method of preparing a mass of ferromagnetic particles each comprising an iron core and a spray-deposited layer of thermoplastic encapsulating said core wherein said mass has a wide range of particle sizes therein and a substantially uniform thickness of thermoplastic on all of said particles regardless of their size comprising the steps of: classifying said cores into batches of approximately the same particle size; spray-depositing a predetermined thickness of said thermoplastic onto the particles in each batch; and thereafter mixing the several batches together to form said mass.

Claim 19

A method of preparing a mass of ferromagnetic particles each comprising an iron core and a spray-deposited layer of thermoplastic encapsulating said core wherein said mass has a wide range of particle sizes therein and a substantially uniform thickness of thermoplastic on all of said particles regardless of their size comprising the steps of: classifying said cores into batches of approximately the same particle size; spray-depositing a predetermined thickness of said thermoplastic onto the particles in each batch; and thereafter mixing the several batches together to form said mass.