GB743792A - Improvements in or relating to the production of magnetisable powder suitable for the manufacture of permanent magnets - Google Patents

Abstract

Magnetisable Fe-base alloys containing a minor proportion of Co and/or Ni are produced in the form of powder consisting of particles of mean size not greater than 1 micron in the greatest dimension by mixing powdered Fe oxide with an organic salt of Co and/or an organic salt of Ni, which salts are decomposable between 300 DEG C. and 425 DEG C. for example formate, acetate or oxalate, mixing being carried out so as to obtain a uniform dispersion of the salt or salts in the mass of oxide. The mixture is then heated in a reducing atmosphere in the range 300 DEG C.-425 DEG C. for 2-3 hours. 0,5-5 per cent of finely divided Zn may be included in the initial mixture in which case reduction is effected in 1-2 hours. Finely divided Mg or Al may also be added to decrease the time required for reduction as described in Specification 743,791. Other metals such as Cu may also be added, e.g. in the form of organic salts. The organic salt or salts used may be added in the form of finely divided powder or as a solution in a suitable liquid the resulting paste being dried and crushed before reduction to metal. The Fe oxide used is preferably Fe2O3 in the anhydrous or hydrated form. The mixture may be subjected to agitation during reduction as by passing hydrogen, the preferred reducing agent, through the powder at the reduction temperature. The resulting powder preferably contains 5,0-35,0 per cent Co or Ni or both together in the range 10-40 per cent.