BESSEMER PROCESS FOR MAKING STEEL. The boldest and most noted attempt which has yet been made to improve on the older methods of making both malleable iron and steel, is that of Mr. Henry Bessemer, whose process was patented in 1856. Bessemer's first idea was to blow air through molten east-iron till the whole of the car bon was oxidized when malleable iron was required, and to stop the blowing when a sufficient degree of decarimrization was effected in order to produce steel. He has hitherto failed to produce malleable iron of the least service by his process, so that, as a metallurgical operation, it is at present confined to the manufacture of steel. But nei ther can serviceable steel be made by the plan first specified by Bessemer, except from the best charcoal iron. such as the Swedish. In England, where charcoal iron is not used for this purpose, the process can only be successfully conducted by first oxidizing the whole of the carbon and silicon, and then restoring the proper amount of carbon the addition of a small quantity of it peculiar cast-iron of known composition, called viegelekien. Moreover, hematite pig is the only kind of English iron which can be employed, as that made from clay iron-stone contains too much phosphorus and sulphur. The getting rid of these two elements and silicon is the most formidable difficulty which the steel-manufacturer has to encounter.
The various steps in the Bessemer process, as at present conducted, are as follow: Pig-iron is melted either inn cupola or reverberatory furnace, and run in the liquid state into a convcrtino vessel. This converter, or " kettle," as it is called in Sheffield, is of wrought-iron, lined either with fire-brick or with a siliceous material called '• ganister," and is suspended on trunnions, so as to admit of its being turned from an upright to a horizontal position by means of hydraulic apparatus. The capacity of a converter varies from three to ten tons. In the bottom there are seven tuyeres, each with seven holes of one half inch in diameter, through which atmospheric air is blown with a pressure of 15 to 20 lbs. per sq. inch by a blowing-engine. The molten iron in the converter is therefore resting, from the first, on a bed of air, the strength of the blast being sufficient to keep it from falling•through the tuyeres into the blast way. During the blowing off
of the carbon at this stage, a striking and magnificent effect is produced by the roar of the blast, and the volcano-like shower of sparks and red-hot fragments from the mouth of the converter, as well as by the dazzling splendor of the flame. In about 15 or 20 minutes, the whole of the carbon is dissipated. The first "blow" being over, the colt verter is lowered to a horizontal position, and presently a red stream of molten spiegel eisen is run into its mouth, till it amounts to from 5 to 10 per cent of the whole charge. As already stated. the spiegeleisen restores the proper amount of carbon to produce steel; and after it is added, the blast is again turned on for a few minutes to secure its thor ough incorporation. There is a circular pit in front of every two converters, with a hydraulic piston in its center, and on its counterpoised arm a large ladle is hung, so that it eau sweep the whole circumference. Round this the ingot molds are arranged, and the hydraulic machinery is so conveniently planned that, simply by moving levers, a man standing on a small platform can empty the contents of the huge converters into the ladle, raise or lower the ladle itself, and turn it round from point to point, so as to fill the molds by means of a plug in its bottom. Steel made in this way is not suffi ciently dense, and accordingly the molds are lifted off the ingots by means of a hydrau lic crane, and the latter removed while still hot, and condensed under heavy steam hammers. After this, they are rolled into rails, tires, plates,' and' other heavy objects. for which this steel is suitable. Although, as already said, Bessemer steel will not do for tools and cutting instruments, nor even for such comparatively coarse objects as the springs of railway wagons, yet the great value of the invention is unmistakably shown by the fact that 500,000 tons of steel are now annually made by this process in Great Britain, the total number of converting vessels in use being 91, and their aggregate capacity 467 tons. Large quantities are also manufactured by it in Sweden, Russia, Austria, Prussia, Belgium, and France. It is likewise extensively employed in America. In an experimental trial, said to be quite fairly conducted, a Bessemer steel rail lasted fully longer than 20 iron ones. See IRON.