|Aluminium is largely employed in the iron and steel industry, as when it is added to molten steel (a few ounces per ton) it removes the dissolved gases to a large extent, and thereby prevents the development of blowholes in castings. In America, aluminium is extensively used in the place of copper for electrical transmission. It is also employed in the production of carbon-free chromium, manganese, molybdenum, ferro- titanium, ferro-vanadium, ferro-boron, manganese-copper, manganese-titanium, chromium-manganese, etc. The metallic oxide or mixture of oxides is reduced by means of a slight deficit of granulated aluminium, the reactions being carried out in large magnesia-lined crucibles as described previously. A mixture of powdered aluminium and granulated rolling-mill scale (Fe3O4), known by the registered name of thermit, is extensively used in welding operations. When fired in the usual way the iron oxide is rapidly reduced to metallic iron, and so much heat is developed that both the iron and alumina are produced in the liquid state. Tram- and railway-line sections may be joined, and broken engine-frames, driving-rods, crank shafts, etc., may be repaired by igniting a charge of thermit and allowing the molten iron to flow around the place at which a join is to be effected. |
The light aluminium alloys containing a high percentage of aluminium are largely used for constructional purposes, e.g. for parts of motor-cycles, motor-cars, and aeroplanes. The salts of aluminium are non- poisonous, and hence aluminium is used to a considerable extent in the manufacture of kitchen utensils, particularly for army use, and is coming into use in the construction of chemical plant. Aluminium cannot be satisfactorily soldered, despite the large number of solders that have been patented for the purpose. It must be riveted or welded.
Aluminium powder enters into the composition of certain explosives.
Thus, ammonal contains 93-97 per cent. NH4NO3, 4-6 per cent. Al, and 0-1 per cent, moisture, and is a good mining explosive and high explosive for shells. Ammonal B contains 94-96 per cent. NH4NO3, 2.5-3.5 per cent. Al, 2-3 per cent, wood charcoal, and 0-1 per cent moisture. Another aluminium explosive contains 85.5 per cent. NH4NO3, 8 per cent. Al, 2.5 per cent, carbon (hydrocarbon or nitrohydrocarbon), and 4 per cent. K2Cr2O7.