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Iron-based permanent magnets and their fabrication as well as iron-based permanent magnet alloy powders for permanent bonded magnets and iron-based bonded magnets

  • US 6,338,761 B1
  • Filed: 02/01/2000
  • Issued: 01/15/2002
  • Est. Priority Date: 12/10/1993
  • Status: Expired due to Term
First Claim
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1. A method for manufacturing an iron-base permanent magnet consisting of fine crystal aggregates of mutually distributed magnetically soft and hard magnetic phases, comprising:

  • (a) providing a molten metal mixture whose composition is represented by the formula Fe100−

    x−

    y−

    z−

    a
    CrxByRzCoa, wherein R is Pr or Nd or mixtures thereof and wherein x, y, z and a satisfy the following values;

    0.01≦

    x≦

    at % 15≦

    y≦

    30 at % 3≦

    z≦

    6 at % 0.01≦

    a≦

    30 at %;

    (b) rapidly solidifying said molten metal mixture into an amorphous material or essentially amorphous material containing fine crystals dispersed in an amorphous matrix, and then (c) heat treating the resulting rapidly solidified material for crystallization of the amorphous material or the essentially amorphous material at a heating rate between 10°

    C./min and 50°

    C./sec from near a temperature at which crystallization starts to an isothermal heat treatment temperature of 600°

    C. to 750°

    C. to produce a magnetically hard material wherein a soft magnetic phase consisting of α

    -iron and a ferromagnetic phase having iron as a main component and a hard magnetic phase having a Nd2Fe14B tetragonal crystal structure coexist in the iron-base permanent magnet, provided that the hard magnetic phase having the Nd2Fe14B tetragonal crystal structure is not a primary phase of said iron-base permanent magnet, the constituent phases of said iron-base permanent magnet having a mean crystal size within the range of 1 nm to 30 nm.

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