|
|
|
|
|
  |
|
 |
  |
We serve various industries with our high quality,
energy efficient, environment friendly, fully automized and cost
effective induction melting furnace "FERmelt".
|
 |
 |
Electric Arc Furnace
Electric arc furnace is important type of electric
furnace which has its beginning in France whose modified version was
manufactured in early twentieth century. Initially they were used for
small purposes but now they are also used in big industries. Configuration An electric arc furnace is mainly used for making steel and consist of devices like refractory-lined vessel and electrodes. Electrodes are normally round in section and comes in segments with threaded couplings, so that as the electrodes wear, new segments can be added. The arc forms between the charged material and the electrode. The charge so formed is heated both by current passing through the charge and by the radiant energy evolved by the arc. Through automatic positioning system electrodes are raised and lowered. For positioning electric winch hoists or hydraulic cylinders are used. The regulating system maintains an approximately constant current and power input during the melting of the charge, even though scrap may move under the electrodes while it melts. The mast arms holding the electrodes are used to convey the current to the electrode holders. The transformer is installed in a vault to protect it from the heat of the furnace. The refractory lined vessel having a removable roof is separated from the electrical system. The bottom of the furnace, is lined with refractory bricks and granular refractory material. There is a tilting platform on which the furnace is built so that the liquid steel can be poured into another vessel for transport in the steel making process. To prevent the liquid steel from the contaminants like nitrogen and slag modern furnaces have a bottom tap-hole on the spout. In some of the latest plant there are two shells with a single set of electrodes that can be transferred between the two; one shell preheats scrap while the other shell is utilized for meltdown. To produce a ton of steel in an steel electric arc furnace lot of power is required. Normally for larger purpose 400 kilowatt-hours per short ton or about 440 kWh per metric ton (1.5 kJ/g) of electricity is required. Operation Scrap metal is delivered to a scrap bay, located next to the melt shop. The furnace is filled with the scrap. In some double-shell furnaces, the scrap is charged into the second shell while the first is being melted down, and pre-heated with off-gas from the active shell. After putting the scrap inside furnace the roof again cover the top of the furnace where the melt down goes on. The electrodes are lowered onto the scrap, an arc is struck and the electrodes are then pushed into the layer of shred at the top of the furnace. Voltage selected for this level of operation is usually small. Low voltages protect the roof and walls from excessive heat and damage from the arcs. After reaching the base of the furnace and the electrodes can be raised slightly, thereby increasing the length of the arcs and increasing power to the melt. This helps in the formation of molten pool even more rapidly. Modern furnaces are designed with some additional features. In this oxygen is pushed into the scrap. sometimes chemical heat is provided by wall-mounted oxy-fuel burners. Both processes accelerate scrap meltdown. The formation of slag is an important part of steel making which floats on the surface of the molten steel. Slag not only acts as thermal blanket but also reduce erosion of the refractory lining. For a furnace with basic refractories causes the slag to foam, allowing greater thermal efficiency, and better arc stability and electrical efficiency. Once srap has been completely melted down, often another bucket of scrap is charged into the furnace and melted down. After the second charge is completely melted, refining operations take place to check and correct the steel chemistry and superheat the melt above its freezing temperature in preparation for tapping. Once the temperature and chemistry are correct, the steel is tapped out into a preheated ladle through tilting the furnace. Applications Electric Arc Furnace has following applications:
|
 |
