The Smelting of Titaniferous Iron Ores 



45 



the main difference between the average blast-furnace slag and the new 

 slag is that in the latter titania is substituted for the major part of the 

 lime of the former. The slag from the Mclntyre furnace has taken this 

 substitution only part way, and has a considerably lower silica content. 



Slag Gl has more silica than provided for in the charge. In this, 

 the first run with a new lining, the brick was corroded to provide the 

 extra silica. In spite of the high percentage of silica, the slag was nor- 

 mally fluid. 



These slags are invariably black and heavy. The weight is accounted 

 for by the high content of titania, the specific gravity of rutile (Ti02) 

 being 4.2. An examination under the microscope shows the black 

 colour to be due to a multitude of minute particles of iron oxide, which 

 make it opaque as well. In one of the slags, well formed crystals were 

 produced, but their opacity made an optical examination impracticable. 



The reduction of the lime to the position of a minor constituent is 

 the feature that makes this slag radically dilTerent from those used here- 

 tofore. Dr. Rossi in his experimental run had similarly low percentages 

 of lime, but reduced the silica correspondingly, and considered titania 

 to be the equivalent of so much silica in the chemical reactions involved. 

 In the present case, the titania acts as so much lime. 



It is probable, though not yet proved in this investigation, that the 

 comparatively high percentage of magnesia tends to make the slags more 

 fluid. If so, this will conform to the unanimous conclusion of those who 

 have already investigated this point in connection with titania-bearing 

 slags. The percentage of alumina present, too, is near the amount 

 commonly considered beneficial in a slag. 



*Stoughton, Bradley. — "Metallurgy of Iron and Steel," page 104. 



The proportions of carbon and silicon in the pig-iron produced in 

 these tests does not conform strictly to any of the recognised standards. 

 From a consideration of the physical properties as given further on, it 



