Magnetic Permeability of various Alloys of Iron. 



109 



it will be seen that 1310 B contains 1*5 per cent, more carbon than 1379 D. 

 Again, 1379 D/2 has low carbon, and the specimen marked 30, with practically 

 the same amount of manganese, has upwards of 1 per cent, more carbon ; the 

 former specimen is non-magnetic, but the latter is slightly magnetic, as also is 

 598, with 18 '5 per cent, of manganese, and 1-54 per cent, of carbon. In the low 

 manganese steels, carbon, as might be expected, decreases the magnetic induction, 

 as will be seen by comparing specimen 4147 on Plate III., and 1420 on Plate V., 

 both having 1 per cent, of manganese, but the latter having higher carbon. 

 Even up to 3| per cent, manganese steel the presence of carbon injuriously 

 affects the magnetic condition as seen on comparing 1379 B and 1381 in the 

 above table. The magnetic measurements of these specimens have been repeated- 

 with concordant results. The hardness of these specimens, as tested by the file, 

 precisely agrees with their relative magnetic conditions : thus the specimen 1381 

 is considerably harder than 1379 B; and 1379 I) harder than 1310 6; whilst 

 598 and 30 are softer than 1379 D/2. The condition in which the carbon exists 

 in these steels is obviously very im^jortant ; the chemical analyses given does not 

 show this, and this point requires further elucidation. 



The next table gives the permeability and hysteresis loss for those manganese 

 steels given in Plate III. 



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



The permeability of the last specimen was too small to be measured as will be 

 seen from Plate III. The rapid fall of permeability between 2^1- and 4 per cent, 

 of manganese is remarkable ; beyond this percentage the hysteresis loss diminishes, 

 owing to the steel passing into a non-magnetic state. We will next take the alloys 

 of iron and nickel. 



E2 



