Drawing of Side-Blown Converter in Blowing Position, Showing Edge of Metal Even with Row of Tuyères
Little of great moment in the electric furnace line developed during the nineteen years which followed. Then, in 1898, Stassano in Rome, Italy, constructed a furnace in which three carbons gave an electric arc above the surface of the bath. About the same time, Heroult, a Frenchman, was developing the electric furnace which to-day has become so well known in this country, and which bears his name. Other well known furnaces of the arc type are the Gronwall-Dixon, the Snyder, the Girod and the Rennerfelt.
In general, electric furnaces have more or less round steel shells with shallow brick, magnesite or sand-lined hearths, and sidewalls and removable roofs of brick. Heat, of course, is furnished electrically. In most of them long carbon electrodes are lowered through holes in the roof until the lower ends strike an arc with the metal on the hearth. The number of carbons may be from one to four or more depending upon the style and size of the furnace and the manner in which electrical connections are made. All of the furnaces mentioned have been used for the production of steel for castings and the Heroult and Girod are in use in larger sizes for electric steel for rails and miscellaneous products. The steel is first cast into ingot molds and is later rolled down into bars, rods, etc.
A Gronwall-Dixon 5–Ton Electric Furnace Tapping
First Experimental Arc Electric Furnaces Patented by Sir William Siemens in 1879
All of the above use carbon electrodes and are known as “arc” furnaces. There is a distinctly different type of furnace which, also, is in use in commercial sizes. This is the “induction” furnace. In this, what is known to electricians as a secondary current is “induced” in the bath itself and heats the metal. Of this type the Kjellin and the Rochling-Rodenhauser are the best known in this country. While they are in use in the larger sizes for production of steel for ingots, these two furnaces do not seem to have been used to any extent for metal for steel castings.
The details of construction of the furnaces which are used for metal for castings are more or less different, but they are not of particular interest to us. The working of all is similar and a general description should suffice.