ALUMINUM STEEL.
When a heat of steel is boiling violently, is wild, and unfit to be poured, the addition of a minute quantity of aluminum will have the effect of quieting it quickly. Half an ounce to an ounce of aluminum to a ton of steel will be enough usually, and for this purpose aluminum has become useful to steel-makers. If a little too much aluminum be added, the ingots will pipe from end to end; therefore the use of aluminum is restricted to small quantities. Experiments have shown that a considerable percentage of aluminum adds no good properties to steel; therefore aluminum steel so called may be treated later under a different heading.
IV.
CARBON.
Of all of the abundant elements of nature carbon is presented in the greatest variety of forms, and admits of the greatest number of useful applications.
In the form of the diamond it is the hardest of substances, and is the base used in determining the comparative hardness of all others.
In the form of graphite it is soft and smooth, and is one of the best and most durable of lubricants.
In the form of soot it is probably the softest of solids.
In the form of coal it is the one great and abundant fuel of the world, while as graphite again it is one of the best of refractory materials.
Hard, soft, highly combustible, almost infusible, refractory, it lends itself to the greatest variety of useful applications. To the iron- and steel-maker or worker it is simply indispensable; as charcoal or coke it is the fuel of the smelter; as gas, either carbon monoxide or as a hydrocarbon, it is the cheapest and most manageable fuel for melting and for all operations requiring heat.
As graphite, plumbago, mixed with a little fire-clay as a binder, it is the best material for crucibles in which to melt metals; as soot it forms the best coating for moulds into which metals are to be cast.
Durable beyond almost any other substance, it would make the very best paint for metal structures if there were any known way to make it adhere.