Electric Arc Furnaces. Electric arc furnaces are often used in large steel foundries and steel mills. The metal is charged into the furnace, with additives to make recovery of slag easier, and heat to melt the metal is produced with an electric arc from three carbon or granite electrodes.
The electric arc furnace is lined with refractories which slowly decompose and are removed with slag. Electric arc furnaces also usually employ air emissions equipment to capture most air pollution.
Induction Furnaces. Induction furnaces are the most widely used type of furnace for melting iron and are increasingly popular for melting non-ferrous metals. They are popular because they provide excellent metallurgical control and are relatively pollution free. Coreless induction furnaces are used for smaller (5-10 ton) operations. In coreless induction furnaces, refractory lined crucibles are surrounded by water-cooled, copper coils.
For larger quantities, channel induction furnaces are used. In these furnaces the copper coils are surrounded by inductors to promote metal melting. Channel furnaces are commonly used to hold the molten metal prior to casting.
Induction furnaces use alternating currents to create heat and melt the metal. The refractories are usually made of silica, alumina or magnesia. They break down over time and become part of the slag.
2.Find in the text English equivalents to the following words and word combinations:
3. Quantities, for, larger, furnaces, are used, induction, channel.
4. Fill in the gaps with the following verbs in appropriate tense form according to the meaning:
to make, to surround, to use, to employ, to remove, to line, to use, to charge
1. Electric arc furnaces _____ in large steel foundries and steel mills.
2. The metal _____ into the furnace.
3. The electric arc furnace _____ with refractory which slowly decompose and _____ with slag.
4. Coreless induction furnaces _____ for smaller operations.
5. Refractory lined crucibles _____ by water cooled, copper coils.
6. Electric arc furnaces usually _____ air emissions equipment to capture most air pollution.
7. The refractory _____ of silica, alumina or magnesia.
5. Answer the following questions:
1. Where are electric arc furnaces used?
2. What do electric arc furnaces usually employ?
3. What is the most widely used type of furnaces?
4. Why are induction furnaces popular?
5. When are channel furnaces used?
1. Read and translate the following text:
Cupola furnaces are the oldest type of furnaces used in foundries. They are tall and roughly cylindrical and are most often used for melting iron and ferroalloys.
Alternating layers of metal and ferroalloys, coke, and limestone are fed into the furnace from the top. Coke makes up 8 - 16% of the total charge to provide the heat that melts the metal. Limestone is added to react with impurities in the metal and floats to the top of the metal as it melts. As in steel melting, this limestone/impurities combination is called slag. By floating on top of the metal while it melts, the slag protects the metal from oxidation.
Cupola furnaces are lined with refractories, or hard, heat resistant substances such as fire clay, bricks or blocks. The refractory protects the furnace shell from abrasion, heat and oxidation. Over time the refractory breaks down and eventually becomes part of the slag.
Cupola furnaces are usually attached to emissions control systems to capture air emissions. Usually, the air emission systems use either high energy wet scrubbers that use water to remove air pollution from the gas stream or dry bag house systems that use fabric filters to capture the emissions.
2. Find in the text English equivalents to the following words and word combinations: