STEEL, MANUFACTURE OF. Recent Improvements.—The one notable improvement in the manufacture of steel in the past ten years has been the successful introduction of the basic process, both open-hearth and Bessemer, the invention of the late Sidney Gilchrist Thomas. In improvement in mechanical details of the manufacture, with the view of dimin ishing the amount of labor and of increasing the output of a single plant, the record of the past ten years has been one of extraordinary development. In Bessemer works, the use of fluid metal direct from the blast furnaces, without remelting in cupolas, has become most general. A notable invention in this department is that by the late Capt. William R. Jones, of the metal mixer, an immense tilting vessel, lined with fire-brick, in which several ladlefuls of iron from different blast furnaces are poured arid mixed, and from which the metal is drawn off as required into other ladles, from which it is poured into the converters. The converters themselves have underaone no essential change, except increase of size. A capacity of 15 tons to the heat is now adopted in the latest works. The old casting pit, with its ingot molds, ladle crane, etc., immediately in front of the converters, is being done away with, and for it are substituted ingot molds placed on cars, and an overhead traveling crane, which carries the ladle of melted steel from the converters to a point above the ingot molds standing on ears at any point in the track running lengthwise through the converter house. This arrangement has been adopted in the latest built works, those of the Maryland Steel Co., at Sparrow's Point, Md., and is about being used in the reconstruction of the Edgar Thomson Works. The ingots, with the metal in their in terior still fluid, are drawn by a locomotive to the " stripper ;" a hydraulic machine strips them—that is, pulls the ingot molds off from them, leaving them standing on the cars. When cool enough to be handled by the crane tongs. they are lifted by a hydraulic crane, and placed, still in a vertieal'position, in the " soaking pits," the invention of Mr. Gjers, of Middlesborough, England, which are underground fire-brick receptacles, heated by the ingots themselves. In Hainsworth's modification of these pits, a small regenerative furnace is
placed adjacent to them, by which they may be heated when necessary by the burning of fuel. When the heat of the ingots has been equalized in these pits, the fluid interior having solidified while the comparatively cool exterior is heated to a yellow heat, they are ready for rolling. In most modern mills they are rolled directly from the ingot into a rail, by passing through two or more stands of rolls in rapid succession, without reheating or cutting into blooms. A four-length rail is usually made, which is cut into rails 30 ft. in length a one operation by five hot saws, which simultaneously make the four rails and the two crop ends. The handling of the rail while passing through the rolls is done entirely by machinery, the invention of Capt. Robert W. Hunt, no manual labor whatever being required to lift or turn either ingot, bloom. or rail. Descriptions of the process of rolling, as adopted at the Edgar Thomson Works, Braddock, Pa., and at the Illinois Steel Co.'s works at South Chicago, are given by Captain Hunt in his presidential address before the American Society of Mechani cal Engineers, in November, 1891.
The Basic Process.—(See Messrs. Thomas & Gilchrist's paper on "The Manufacture of Steel and Ingot Iron from Phosphoric Pig Iron," which was read before the Society of Arts, i in London, in 1882.) The Bessemer vessel is lined with magnesian lime, which has been previously subjected to an intense white heat, and so brought to a condition of density, tenacity, and hardness as far as possible removed from the conditions of the material generally known as "well burnt lime," and more closely resembling granite or flint. This material, which for brevity is known as "shrunk lime" (as in course of preparation it shrinks to one-half the bulk of ordinary lime), is used either in the form of bricks or in admixture with tar, as a rammed or " slurry" lining, this being substituted for the ordinary silica brick or siliceous ganister lining of the hematite process.