Page:Popular Science Monthly Volume 19.djvu/834

814 been passed through the other regenerator, it burns, giving out intense heat.

There are two methods now in use for the production of steel in the reverberatory furnace, or open-hearth, as it is called. In France, pig-iron and scrap-steel are fused together; in England, pig-iron is decarburized by means of iron-ore, some scrap, however, being generally added for the sake of utilizing it. As in the Bessemer process, the necessary amount of carbon is imparted to the metal by the means of spiegeleisen or ferro-manganese. This process has been largely employed for the production of ship and boiler plates. It has the great advantage that the metal can be kept fluid on the hearth, and its composition adjusted until it is exactly that required.

In 1876 a patent was taken out by M. Pernot, in which it was proposed to produce steel on an open-hearth furnace with a revolving bed, inclined at an angle of 5° or 6° to the vertical. Pig-iron previously heated to redness is placed in the bed of the furnace and covered with scrap-steel. The bed of the furnace is then made to revolve slowly, the pig gradually melts, and the scrap is alternately exposed to the strong heat of the flame, and then dipped under the molten pig iron. In this way the fusion is very rapid, comparatively, the whole mass becoming fluid in about two hours. The process is then completed in the ordinary way. M. Pernot informs me that he has just taken out a patent for an arrangement of his furnace by means of which he can employ gas under pressure, and that within the last few months he has obtained by this means results which have never been equaled before.

The Ponsard furnace aims at combining the advantages of the Bessemer and open-hearth processes. The furnace is so arranged that, by giving it a half-revolution on its oblique axis, the tuyères with which it is supplied may be brought either beneath or above the surface of the bath of metal. By these means the metal can be rapidly decarburized nearly entirely, as in the Bessemer converter, and then, by removing the tuyères from beneath the metal, the final adjustment of the carbon can be made as in the Siemens process. The rapid destruction of the tuyères which is effected is a formidable obstacle to the practical success of this process.

The one important drawback to the Bessemer process was that phosphorus was not in any degree eliminated by it. Notwithstanding this, enormous quantities of steel were made by it; and, within the last three years, means have been devised in the Thomas-Gilchrist, or "basic" process, by which this difficulty has been overcome. In the ordinary Bessemer converter the lining was formed of ganister, a siliceous material, the chemical effect of which was to prevent the elimination of phosphoric acid. Messrs. Thomas and Gilchrist sought a basic material which they could substitute for the ganister, and found a magnesian limestone which worked very satisfactorily. The