STRENGTH OF STEEL. 



365 



TABLE II. TESTS OF PIECES TAKEN FROM 



COMPRESSED STEEL FORGINGS. 



FLUID- 



In the last-mentioned tests of shell steel the metal 

 was all taken from the same ingot. The first set of 

 results are the average of three test pieces forged from 

 the ingot and left in the soft state, while the last three 

 sets of figures are from the metal of a shell which has 

 been forged, turned, bored, and hardened in the usual 

 way, and then fired at an armour plate, from which it 

 rebounded. 



191. Strength of Manganese Steel. The alloy of iron 

 and manganese with a small percentage of carbon, commonly 

 called manganese steel, possesses strength properties 

 which render its use important for very many purposes. 

 Steel containing only small percentages of manganese up 

 to about 1 per cent, are not affected to any noticeable 

 extent by the proporton of manganese present. When 

 the percentage is increased gradually up to about 8 per 

 cent, the ultimate strength of the metal is impaired. 

 But beyond this, up to about 18 per cent., the increase of 

 manganese is accompanied by an increase of strength, 



