Page:Popular Science Monthly Volume 19.djvu/830

810 alternately in the same finery. This furnace, in its simplest form, consists essentially of a shallow quadrangular hearth, formed of cast iron plates. In one side is a tuyère, inclined at an angle of 10° to 15°. The bottom is kept covered with a layer of charcoal. In the Siegen district, a piece of pig-iron, weighing fifty to sixty pounds, is placed on the hearth, having been previously heated; the hearth is then three parts filled with burning charcoal; on it is placed a portion of the cake produced in the last operation, which has been kept hot in burning charcoal, at the back of the furnace. The remainder of the hearth is then filled up with charcoal. The other six or seven pieces into which the last cake was divided are placed on the top. In this process, the production of steel and the reheating of that obtained in the last operation, preparatory to working it under the hammer, are conducted together. The blast is turned on. The piece of pig-iron forms into a pasty mass; cinder, rich in oxide of iron, produced in the latter part of the preceding operation, is then thrown in; a second piece of pig-iron, weighing about one hundred pounds, is added, and afterward four or five pieces of spiegeleisen (cast-iron, containing manganese), weighing each about a hundred pounds, are successively added. If the metal is found to be too much decarburized, more Spiegel is added. In this process, as in the Catalan, it is impossible to obtain a homogeneous product. The principle in both is essentially the same, viz., decarburization by oxide of iron. In this process, as in every other process for the production of steel, manganese is used with great advantage—an advantage which arises from its power of replacing iron in the slag and of forming a slag that is more liquid than one containing iron alone.

The essential difference between the finery and the puddling process consists in the use of a reverberatory furnace, the manipulation of the metal and the regulation of the temperature being thereby greatly facilitated. The decarburization is effected by the addition of oxide of iron produced during rolling, and partially by the air which enters the furnace as the metal melts slowly down; manganese is added during the process. It is important that the temperature should be kept low. It is difficult to weld this steel perfectly, because, probably, the temperature at which it has to be worked is too low to make the cinder sufficiently liquid to enable it to be squeezed out under the hammer to the same extent that it is in the case of malleable iron. This difficulty has, however, been got over by completely fusing the steel before working it, so as to enable the slag to separate completely. In this form metal manufactured by this process has been largely used by Krupp.

The principle which regulates the production of steel by these methods is taken advantage of in the Uchatius process, in which pig iron is first granulated by running it while molten into cold water. The granulated metal is then mixed with about twenty per cent, of roasted