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Electric Furnaces and Their Industrial Applications
Electric Furnaces and Their Industrial Applications Author:John Wright Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: SECTION III Resistance Furnaces And Typical Processes The heat developed in a conductor, such as the core of a resistance furnace, by the passage of an ele... more »ctric current through it, depends upon— 1. The ohmic resistance of the conductor. 2. The magnitude of the current. 3. The duration of its flow. All three quantities are open to regulation in the majority of resistance furnaces, hence the facility with which this type lends itself to exact temperature regulation and control. The temperature of a heating resistance core depends upon the rate of development of heat within it, and upon the rate at which it is capable of dissipating that heat by radiation and conduction. The ultimate fixed temperature of a resistance furnace core is attained when the above two quantities are exactly equal, i.e. when the rate at which heat is dissipated or given off by the conductor is equal to the rate at which it is developed. The limit of temperature attainable in such a conducting core depends, of course, upon the fusing point of the material of which it is composed. An excellent example of the various possibilities of a suitably designed resistance furnace, in which the temperature regulation is well under control, and can be altered with a fair degree of accuracy over an extended range, is to be seen in the various Acheson furnace processes, in whichsilicon and carbon constitute the raw materials under treatment. By certain variations in the conditions and temperatures at which the reactions are brought about, it is possible to produce carborundum, " white stuff," silicon, siloxicon, or graphite, at will. With resistance furnaces generally, and those of the Acheson type, with only a partially independent core, in particular, the question of efficient temperature ...« less