ClIAP. XXVIII.] MANGANESE IN lEON AND STEEL. 
593 
Roberts-Austen explains the effect of manganese on steel in the 
following manner : — 
Manganese having a lower atomic volume (6-9) than iron (7-2) delays 
during cooling the change from the ^, or hard alio tropic variety of iron 
into the «, or soft variety, as well as that of hardening carbon into carbide 
carbon. Hence with equal rates of cooling it tends to increase the pro- 
portion of ^-iron present in cooled iron and steel, and consequently the 
hardness of the metal ' . ' Speaking generally, if the steel contains, 
in addition to carbon, per cent, of manganese, each class of steel would 
be equivalent, as regards tenacity and hardening properties, to the one 
above it ', i.e., it would be equivalent to a steel with more carbon 2. 
Above 7% of manganese appears to prevent entirely the passage of y8-iron 
into a-iron, and since y8-iron cannot be magnetized — the temperature of 
recalescence, at which iron in cooling down changes from the y8 to the a 
form, being also that at which iron on heating up looser- the power of 
being magnetized and passes from the a to the y8 form — , steels with over 
7% of manganese are non-magnetizable. Ewing concludes that ' no 
magnetising force to which the metal is likely to be subjected, in any of 
its practical applications, would produce more than the most infini- 
tesimal degree of magnetisation ' in Hadfield's manganese-steel.^ That 
high manganese may to a certain extent counteract the deleterious 
effects of phosphorus is explained by the fact that the manganese 
phosphide has the formula Mn3P2, whilst that of the iron phosphide is 
FesP, so that the manganese can take up twice as much phosphorus as 
the iron. When in the phosphide condition the phosphorus is less 
injurious to the mechanical properties of the steel than when evenly 
disseminated through the steel. 4 
Hadfield ^ has recently patented a manganese-steel containing 
10-40°/o manganese and less than 1% carbon. It is prepared by the 
addition to decarburized iron of ferro-manganese, made in the electric 
furnace, and containing only 2-3% of carbon. Owing to the compara- 
tively low percentage of carbon in the steel, it is less hable to fracture 
during treatment. It is also distinguished by its relatively strong 
magnetic characters. 
1 ' Introduction to the Study of Metallurgy ', p. 121, (1902). 
2 Loc. cit., p. 17H. 
3 Loc. cit., p. 171. 
4 J. A. Mathew.s, ' Mineral Industry ', XI. p. 073. 
5 Electrochemical and Melallargical Induatrt/, July 1907, p. 283. 
