374 



APPLIED SCIENCE 



iron. The flux when melted floats on the liquid iron and 

 absorbs and liquefies its non-metallic residue and the ash of 

 the fuel, so that they may be drawn off by means of the slag 

 holes before the heat is run off. The liquid iron is then taken 

 from the furnace in ladles, and carried by men to different 



molds where it is "poured" 

 (Fig. 186). As the hot iron 

 flows into the mold and cools, 

 it takes the shape of the 

 mold. 



417. Mixing the Iron. 



The best results for strength 

 and elasticity are obtained by 

 mixing a number of carefully 

 selected kinds of iron, as such 

 a mixture gives higher tensile 

 strength than the average 

 strength of the different sam- 

 ples cast separately. When all 

 the carbon in iron is in a com- 

 bined state, the fracture of a 

 freshly broken piece has a 

 silvery white color. When 



FIG. 186. Drawing Iron from 

 Cupola. When the iron has 

 been melted down in the fur- 

 nace it is drawn from the 

 cupola into large ladles which 

 are picked up by the overhead 

 traveling cranes and taken to 

 the flasks where later it is 

 poured. 



only a little carbon is com- 

 bined, most of the carbon particles crystallizing separately, 

 the fracture is gray in color, and the iron is weaker and 

 more fusible. Hence the founder must exercise good 

 judgment in selecting suitable mixtures of different sorts 

 and qualities to obtain the desired strength, softness, hard- 

 ness, toughness, and clearness of grain for different 

 castings. 



