108 



Barrett, Brown & Hadfield — On the Electrical Conductivity and 



Table IV. — Alloys of Iron and Manganese (Plate III.). 



From the above table it will be seen that a great drop takes place in the 

 maximum induction, and a corresponding rise in the coercive force, when the 

 quantity of manganese added to steel is somewhere between 3 and 4 per cent. 

 The sudden rise in coercive force at this point is shown in fig. 12, p. 117. Upon 

 referring to Plate III. the wide difference between the curves for specimens 

 marked 53 and 39 is at once apparent. When the quantity of manganese in the 

 alloy rises to between 7 and 10 per cent., further additions of manganese seem to 

 have much less effect on the magnetic properties of the alloy; a 13 per cent, 

 manganese steel, such as 1338, is practically non-magnetic. Upon referring 

 to Plate II., showing the electric conductivity of manganese steels, the con- 

 ductivity is likewise seen to decrease up to a 7 per cent, manganese steel, and 

 then remains nearly constant up to the highest percentage tried. 



Judging from the specimens here tested, a remarkable feature in the magnetic 

 properties of the high manganese steels is the part played by the i^resence of 

 carbon. Although the specimen marked 1310 B has 1 per cent, more manganese, 

 it is considerably more magnetic than 1379 D. On turning to Group 2, p. 76, 



* These specimens all contain high carbon from 0-78 to 1-66 per cent. See Group 2, series B, p. 76. 

 f The curves in the last four specimens lay so close to the axis H, that the values of retentivity and 

 coercive force were too small to be correctly measured. 



