THE PNEUMATIC PROCESS.
Steel has been made by this process in Germany for a long period, while it has fre quently been produced, both by accident and design, direct from the ore, by using more or less air in the operation of smelting, and more or less carbon (coal) in the conversion from ore to metal.
The most economical and practical application of oxygen for the decarbonization of cast iron is when the metal is fluid and direct from the blast-furnace. It can then be changed from a carburet to a soft iron by the process of oxidization, or by burning out the carbon by passing air through the fluid mass at high-pressure. This process is the same in effect as that which is produced in the puddling-furnace with so much more labor and cost. By that process, however, the pig metal is remelted (as it is frequently done in this) and the fluid mass is exposed to currents of flame and air passing over the surface by constant stirring, as formerly described. By the pneumatic process the air is blown with great force up through the molten metal, and, of course, accomplishes the same object more completely and with much greater economy.
The great difficulty has been in the mechanical appliances for effecting this purpose, and the experience required for the proper regulation of the blast, the time of deoxidi zation, and the improvement of the products by the requisite admixture of manganese, which is a necessity, for the production of good iron or steel.
A great many patents have been obtained in this country and Europe for the employ ment of air, steam, or gas in the deoxidization of cast iron. But we do not think any patent can cover a process which has been in use for ages. The mechanical means, however, of applying air to this purpose is open to competition, and always has been.
Henry Bessemer, of England, has been the most successful in this application, and deserves great credit for the practical manner in which he has accomplished the great revolution in the manufacture and use of steel now going on, by which it may become less valuable than pure iron in regard to cost.