New ductile Cr-Co-Fe permanent magnet alloys for telephone receiver applications

Abstract

Cr-Co-Fe permanent magnet alloys have been investigated for potential replacement of Remalloy in the U-type ring armature telephone receiver. Of particular interest would be an alloy which could be cold drawn into cup shape. Small additions of Al, V, Nb, Ti and Zr were added to the basic 28%Cr–15%Co–Fe ternary in an attempt to suppress γ phase formation and improve cold formability. As a result of extensive investigation we have discovered two Zr bearing alloys that are highly promising for fabrication as receiver magnets. One alloy consists of 0.25%Zr–1%Al and the other 0.25%Zr–0.25%Ti–1%Nb. After suitable heat treatment they yield values of Br=9600 G, Hc=460 Oe, BHmax=1.9×106 GOe and Br=8900 G, Hc=440 Oe, BHmax=1.8×106 GOe respectively.