Every-day Science: Volume 6. The Conquest of Nature

by Henry Smith Williams; Edward Huntington Williams

In deciding the exact moment when the blast shall be turned off, this workman is guided entirely by the sense of sight. Mounted on a platform commanding the best possible view of the mouth of the converter and wearing green glass goggles of special construction, this man watches the change of color in the flame until a certain shade is reached—a shade that to the ordinary untrained observer does not differ in appearance from that of a moment before—when he gives the signal to shut off the blast. When this signal is given the contents of the converter is no longer common-place cast iron, but steel, ready to be molded into rails, boilers, or a thousand and one other useful things.

The contents of the converter may now be drawn off as liquid steel into molds of any desired shape and size, and when cooled will be ready for shipment. But in the great steel factories the metal is not ordinarily allowed to cool completely before being sent to the rolling mills, being drawn off into molds placed along the surface of small, flat cars. These molds are rectangular, ordinarily four or five feet high by less than two feet in diameter. The metal is poured into openings in the top of each mold, and allowed to cool, solidify, and to contract enough to permit the outer casings of the molds to be pulled off by machinery, leaving the glowing "ingots" of steel ready for molding by machinery in the mills.

The process just described is the one by which "Bessemer steel" is made. There is another important process in use, the "open hearth" method, which differs considerably from this; but before considering this process something more should be said of the man whose discoveries made possible the modern steel industry.

SIR HENRY BESSEMER

In the history of the progress of science and invention some one great name is usually pre-eminently associated with epoch-marking advances, although there may be a cluster of important but minor associates. This is true in the history of the modern steel industry, and the central name here is that of Sir Henry Bessemer.

Bessemer was born at Charlton, England, on Jan. 19, 1813. Always of an inventive turn of mind, his attention was first directed to improving the methods then in use for the manufacture of steel, while experimenting with the manufacture of guns. After several years of experimenting in his little iron works near London, he reached some definite results which he announced to the British Association in 1856. In this paper he described a process of converting cast iron into steel by removing the excess of carbon in the molten metal by a blast of air driven through it. This paper, in short, described the general principles still employed in the Bessemer process of manufacturing steel. And although the first simple process described by Bessemer has been modified and supplemented in recent years, it was in this paper that the process which placed steel upon the market as a comparatively cheap, and infinitely superior, substitute for ordinary iron, was first disclosed.

This famous paper before the British Association aroused great interest among the English ironmasters, and applications for licenses to use the new process were made at once by several firms. But the success attained by these firms was anything but satisfactory, although Bessemer himself was soon able to manufacture an entirely satisfactory product. The disappointed ironmasters, therefore, returned to the earlier processes, the inventor himself being about the only practical ironmaster who persisted in using it.

Recognizing the defects in his process, Bessemer set about overcoming them, and at the end of two years he had so succeeded in perfecting his methods that his product, equal in every respect to that of the older process, could be manufactured at a great saving of time and money. But the ironmasters were now skeptical, and refused to be again inveigled into applying for licenses. Bessemer, therefore, with the aid of friends, erected extensive steel works of his own at Sheffield, and began manufacturing steel in open competition with the other steel operators. The price at which he was able to sell his product and realize a profit was so much below the actual cost of manufacture by the older process, that there was soon consternation in the ranks of his rivals. For when it became known that the firm of Henry Bessemer & Co. was selling steel at a price something like one hundred dollars a ton less than the ordinary market price, there was but one thing left for the ironmasters to do—surrender, and apply for licenses to be allowed to use the new process.

By this means, and through the profits of his own establishment, Bessemer eventually amassed a well-earned fortune. Moreover, he was honored in due course by a fellowship in the Royal Society, and knighted by his government.

One other name is usually associated with that of Bessemer in the practical development of the inventor's original idea. That is the name of Robert Mushet, and the "Bessemer-Mushet" process is still in use. Mushet's improvement over Bessemer's original process was that of adding a certain quantity of spiegeleisen, or iron containing manganese, which, for some reason not well understood, simplifies the process of steel making. Mushet, therefore, must be considered as the discoverer of a useful, though not an absolutely essential, accessory to the Bessemer process.