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BELL SYSTEM TECHNICAL JOURNAL 



this respect. Its action may be explained by postulating that its 

 presence decreases the solubility of carbon in iron. The silicon enters 

 the iron lattice as a substitutional element, and as such, is less harmful 

 to the magnetic softness than the interstitial element, carbon, which is 

 removed. Since silicon is also a strong deoxidizer, it will remove 

 oxygen from the iron. These reactions do not completely eliminate the 

 carbon and oxygen, and consequently, although a noticeable increase 

 in magnetic softness is obtained, the high values of permeability 

 achieved with the more efficient methods of purification are not 



10000 



3 



< 



O 8000 



6000 



4000 



2000 



4 5 6 



H IN OERSTEDS 



10 



Fig. 3 — A comparison of the magnetization curve of cominercial 4 per cent silicon 

 steel" with that of Arnuo iron^^ showing the superiority of the former at low induction 

 densities. 



reached. The improvement attained by this treatment is illustrated 

 in Fig. 3 by comparison of typical magnetization curves for armco 

 iron ^^ and for a commercial 4 per cent silicon steel. ^ 



The second method of producing a purer iron consists of eliminating 

 some of the harmful elements by melting in a high vacuum. ** Under 

 these conditions, the residual carbon and oxygen in the iron will com- 

 bine to form carbon monoxide, which is removed by the exhausting 

 pumps. At the same time, due to the dissociation of the nitrides at the 

 high temperature, the nitrogen is similarly removed. Again, the 



