Considerable excitement was caused at the time the process was invented, not only on account of the time saved, but also because there was such a great saving in fuel.
After the metal has been poured from the converter into molds similar to those shown in [Fig. 159], and has cooled sufficiently to become solid, the molds are stripped off, as shown in [Fig. 160], and the ingots of metal placed in the soaking pits, [Fig. 161]. These pits are somewhat similar to a crucible furnace and are used for reheating ingots before they are slabbed or rolled. Such a furnace is generally made of the regenerative type and is divided into several compartments, each one capable of receiving several ingots which are inserted on end.
Fig. 162.—A Blooming Mill.
From the pit furnace the ingots are taken and rolled into slabs, rails, blooms, or other forms suitable for use. When the plant is equipped with both blast furnace and converter, this is all done without additional heating, but when the plant is not so equipped, the pig iron is melted in a cupola furnace before being put into the converter. A blooming mill is shown in operation in [Fig. 162].
Fig. 163.—Open-hearth Furnace, from the Charging Side.
Fig. 164.—Sectional View of an Open-hearth Furnace.
184. The Open-hearth Process.—[Fig. 163]. Here again the process depends on the type of furnace. Open-hearth steel is produced with a reverberatory furnace, and the heat is supplied by regenerative gas and air. The furnace is built mostly of brickwork with the exception of the supporting beams, doors, tie rods, and hearth castings, which are made of cast iron, wrought iron, or steel. All brickwork that comes in contact with the intense heat is made of silica brick, manufactured from rock crystals, flint, or other varieties of quartz rock with about two per cent of quicklime. The roof of the furnace slopes toward the center, so that when the air and gas enter they are directed downward on the charge of metal. The bottom or hearth is constructed of heavy steel plates riveted together and supported on I beams. This bottom is first covered with a layer of brick, then sand is applied to about the thickness of one inch and well rammed down, then other layers of brick and sand are added until the thickness is about 14 to 16 inches. This bottom requires repairing with more sand between successive heats. Figure [164] shows a cross section through the center of the charging and discharging openings.