FERROMANGANESEA master alloy of manganese and iron used for deoxidizing steels and for adding manganese to iron and steel alloys and bronzes. Manganese is the common deoxidizer and cleanser of steel, forming oxides and sulfides that are carried off in the slag. Ferromanganese is made from the ores in either the blast furnace or the electric furnace. Standard ferromanganese has 78 to 80% manganese. British ferromanganese contains about 7% carbon, but the content in the U.S. alloy is usually 5 to 6.5%. Low-carbon ferroman-ganese is also marketed containing 0.10 to 1% carbon. Low-phosphorus ferromanganese contains less than 0.10% phosphorus. The alloys are marketed in lumps to be added to the furnace. Spiegeleisen is a form of low-manganese ferromanganese with from 15 to 30% manganese and from 4.5 to 5.5 carbon. The German name, meaning mirror iron, is derived from the fact that the crystals of the fractured face shine as mirrors do. Spiegeleisen has the advantage that it can be made from low-grade manganese ores, but the quantity needed to obtain the required proportion of manganese in the steel is so great that it must be premelted before it is added to the steel. It was used for making irons and steels by the Bessemer process. Grade A spiegeleisen has 19 to 21% manganese and 1 silicon; Grade B has 26 to 28% manganese and 1 silicon. The melting point is from 1950 to 2265°F (1066 to 1240°C).
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