MAGNETIC ALLOYS 



117 



are added. In designating ternary permalloys the same scheme is 

 extended, so that the name gives everything except the iron content, 

 and this is obtainable by difference. Thus, 3.8-78.5 Cr-permalloy 

 contains 3.8 per cent chromium, 78.5 per cent nickel, and 17.7 per cent 

 iron. 



The perminvar region, enclosed by the curved line, contains those 

 compositions that require baking to develop completely their charac- 

 teristic magnetic properties. The specific compositions of these 

 alloys are indicated by two prefixed numerals, the first indicating the 

 nickel and the second the cobalt percentages, respectively. Thus 

 the 45-25 perminvar alloy contains 45 per cent nickel, 25 per cent 

 cobalt, and 30 per cent iron. Another alloy of the perminvar group, in 

 which the nickel and cobalt percentages are the same as the alloy 

 just mentioned, but which contains 7 per cent molybdenum and 23 

 per cent iron, is designated as 7-45-25 Mo-perminvar. 



In the iron-cobalt series of alloys the composition 50 per cent iron 

 and 50 per cent cobalt has been developed for commercial use. This is 

 the permendur alloy, indicated in the triangular diagram in Fig. 1. 

 This alloy is difficult to cold roll, but the addition of 1.7 per cent 

 vanadium improves the mechanical properties and makes it sufficiently 

 ductile to roll into thin sheets. The same system has been followed in 

 designating this alloy as in the case of the permalloys. Thus 1.7 

 V-permendur is an alloy containing 1.7 per cent vanadium with iron 

 and cobalt in equal proportions. 



Table I lists the designations and compositions of those alloys, 

 developed for particular purposes, which are discussed more fully in 

 the remainder of this paper. 



TABLE I 

 Designations and Compositions of Some Magnetic Alloys 



Designation 



78.5 permalloy 



80 permalloy 



45 permalloy 



3.8-78.5 Cr-permalloy . 

 3.8-78.5 Mo-permalloy . 

 2-80 Mo-permalloy . . . . 



45-25 perminvar 



7-45-25 Mo-perminvar. 



Permendur 



1.7 V-permendur 



Composition, Per Cent 



Ni 



78.5 



80 



45 



78.5 



78.5 



80 



45 



45 



Fe 



21.5 



20 



55 



17.7 



17.7 



18 



30 



23 



50 



49.15 



Co 



25 

 25 

 50 

 49.15 



Cr 



3.8 



Mo 



1.7 



Ni = nickel; Fe = iron; Co = cobalt; Cr = chromium; Mo = molybdenum; 

 V = vanadium. 



