490 



ENGINEERING MATERIALS. 



CHAP. XV. 



able part of the phosphorus is oxidized; all oxidized products unite with the slag. Second or 

 clearing stage, occupying about IO minutes, during which the remainder of the silicon and manga- 

 nese, and more of the phosphorus are oxidized and removed from the pig iron. Third or boiling 

 stage, occupying about 30 minutes, in which nearly all the carbon is removed and most of the 

 remaining phosphorus is removed. Last or balling stage, occupying about 20 minutes, in which 

 the metal is gathered by the puddler into balls weighing about 75 to 100 Ib. 



T 



* 



FIG. 2. MOLD FOR ARBITRATION TEST BAR. 



The puddled balls of iron and slag are hammered or are run through rolls to squeeze the slag 

 from the balls, and the resulting bars are called muck bars. The muck bar is again reheated and 

 rerolled and the resulting product is commercial merchant bar. 



Wrought iron when broken in tension shows a fractured section irregular and fibrous. The 

 strength of wrought iron varies with the chemical composition, the mechanical work and heat 

 treatment it has received. The strength of wrought iron is given in Table I, and the specifications 

 for wrought-iron bars and plates as adopted by the American Society for Testing Materials are 

 as follows: 



