In the ladle in which metal discharged from an electric arc furnace is molten and secondarily refined for steel making, an arc heating by a graphite electrode is performed. To reduce the consumption rate of electrodes and the cost of electric energy to the lowest degree possible, it is important to suppress oxidative ablation at the end and peripheral surfaces of the graphite electrodes heated to high temperatures during melting and refining. The present invention solves this issue by spraying cooling liquid over the end and the peripheral surface graphite electrode.
The cooling apparatus of this invention consists of a tube 4 annular into which are projected a plurality pipes 5, the insides of each of which have nozzles 6 facing down the surface of graphite electrode 2. Cooling liquid is sprayed into each nozzle 6 by cooling water flowing down the pipe 5.
The cooling water jetted by each nozzle 6 is sprayed in a downward angle. A large amount of cooling water is reflected, and splashed over the electrode holder 1 and the furnace cover 1, which are made of refractory like chamotte. The splashed cooling waters severely stain and damage the refractory. Furthermore, the thermal conductivity of the graphite electrode itself decreases in a temperature region above about 100 deg C., and it is difficult to cool the lower portion of the graphite electrode which participates in melting and refining.
The graphite electrode in the present invention is sprayed with cooling liquid at the rate thereof optimum for the diameter of the electrode so as to prevent the oxidative ablation of the end surface and the peripheral surface thereof. The cooling performance of the graphite electrode is greatly improved, and the electrode consumption rate is reduced.
It is recommended that you use a high quality graphite electrode of the following type:
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