Plate B 

 (Artificial Irons) 



1. Hypereutectoid steel (carbon 1.10 percent). The carbon content being above the eutec- 

 toid ratio (0.80 percent), pearlite now predominates, with cementite segregating along grain 

 boundaries. Compare plate A, figure 2, in which ferrite predominates. Strong nital etching; 

 X 60. 



2. White cast iron (carbon about 33 percent). The structure consists of dendrites of pearl- 

 ite (black) in a matrix of cementite. Strong picral etching; X 60. 



3. White cast iron; the same as figure 2; X 600. The pearlitic structure of the dendrites is 

 shown. 



4. Gray cast iron (carbon about 3 percent). Under the conditions of cooling and composi- 

 tion (some silicon probably being present) the carbon in excess of that necessary to form pearl- 

 ite is rejected as flakes of graphite. Light nital etching; X 600. 



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