Ferrochrome

From Wikipedia, the free encyclopedia

Ferrochrome is a corrosion-resistant alloy of chrome and iron containing between 50% and 65% chrome. It is a finishing material which contains about (50-70% depending on ore used a the producer) chromium alloyed with iron. Most of the world's ferrochrome is produced in South Africa and India, with increasing amounts coming from Russia, China, central Asia.

Over 80% of the world's ferrochrome is utilised in the production of stainless steel. Stainless steel depends on chrome for its appearance and its resistance to corrosion. The average chrome content in stainless steel is approximately 18%. It is also used when it is desired to add chromium to carbon steel.

Ferrochrome production is essentially a carbothermic reduction operation taking place at high temperatures. Cr Ore (an oxide of chromium and iron) is reduced by coal and coke to form the iron-chromium alloy. The heat for this reaction can come from several forms, but typically from the electric arc formed between the tips of the electrodes in the bottom of the furnace and the furnace hearth. This arc creates temperatures of about 2800°C. In the process of smelting, huge amounts of electricity are consumed making production in countries with high power charges very costly.

Tapping of the material from the furnace takes place intermittently. When enough smelted ferrochrome has accumulated in the hearth of the furnace, the tap hole is drilled open and a stream of molten metal and slag rushes down a trough into a chill or ladle. The ferrochrome solidifies in large castings, which is crushed for sale or further processed.

Ferrochrome is often classified by the amount of carbon it contains. For example low carbon, high carbon and intermediate carbon.