THE USE OF IKON. 



of these elements contributing to strength and hardness in 

 the steel." 



OPEN-HEARTH BASIC STEEL. 



"Distinguishing Terms. -^Fbr convenient distinguishing- 

 terms, it is customary to classify steel in three grades ; ' mild or 

 soft,' 'medium/ and * hard,' and although the several grades 

 blend into each other, so that no line of distinction exists, in 

 a general sense the grades below .15 per cent, carbon may be 

 considered as * soft ' steel ; from . 1 5 to . 30 per cent, carbon as 

 4 medium ' ; and above that, * hard ' steel. Each grade has its 

 own advantages for the particular purpose to which it is 

 adapted. The soft steel is well adapted for boiler-plate and 

 similar uses, where its high ductility is advantageous. The 

 medium grades are used for general structural purposes, while 

 harder steel is especially adapted for axles and shafts, and 



