Photograph from Brown Brothers 

 LOADING STEEL RAILS IN CARS, USING AN ELECTRO-MAGNET CRANE 



Feeding a blast furnace is no small job, 

 measured by the material it has to have. 

 Every day it wants about 800 tons of ore. 

 400 tons of coke, and 100 tons of lime- 

 stone. But its reward to the feeders is 

 about 400 tons of pig iron. It takes an 

 enormous amount of air to make the fur- 

 nace hum fast enough, some 37,500 cubic 

 feet a minute at Gary. The big stoves of 

 the furnace are of checker-like construc- 

 tion, resembling the radiator of an auto- 

 mobile. They are brought to an intense 

 heat, and the air is then passed through 

 their white - hot interstices before it 

 reaches the materials to be melted. Here 

 it makes the coke burn like "blue blazes.'' 



The coke now gives off vast new sup- 

 plies of gas, part of which in turn comes 

 back to heat the stoves, part to drive the 

 big blowing engines, and another part to 

 drive the dynamos which make electricity 

 for operating the machinery of a great 

 steel plant, in the case of Gary. 



Running a blast furnace is indeed an 

 exact science. The whole furnace must 

 be water-cooled like an automobile en- 

 gine, lest even the fire-brick give way 

 under fervent heat. The rule of thumb 

 doesn't go. Exact weights, measures. 



analyses, are necessary. If the slag is 

 too acid, it will leave poor pig iron be- 

 hind ; if it is too limy, it will refuse to 

 melt properly and cause "scaffolding." 

 A classic illustration among iron men of 

 what the rule of thumb results in is the 

 story of the manager who got too little 

 silica and too much limestone in his mix- 

 ture and the owners lost $2,000 while he 

 "thawed out" the "frozen" mass in his 

 furnace, as they say in pig-iron parlance 

 when the stuff refuses to melt. 



Unless the materials are carefully 

 mixed, they will form a "scaffold" as they 

 pass down from the top to the bottom of 

 the furnace and while in the process of 

 changing from solids to liquids under the 

 spell of the heat. Once scaffolding starts, 

 it is in danger of reaching clear across 

 the shaft and damming up the downward 

 flow of the materials or of "slipping" — 

 that is, breaking loose at an inopportune 

 moment. 



IRON THAT FLOWS LIKE MILK 



When the iron, now as liquid as milk, 

 is drawn off. it is pig iron, although under 

 modern practice it may never see a pig 

 mold at all. At some furnaces it is still 



144 



