Chromium acts as a carbide stabilizer in cast iron. Thus it intensifies chilling of cast Iron , Increases strength , hardness and wear - resistance and is conductive to fine grain structure. Most additions of chromium range from 0.15 to 0.90 percent with or without other alloying elements. Chromium of 1.0 percent or more make castings hard to machine. With 3.0 percent chromium, white cast iron is formed. Special Irons to resist corrosion and high temperatures contain as much as 35 percent chromium.
Various types of melting furnaces are used in different foundry shops, depending upon the quantity of metal to be melted at a time, and the nature of work that is carried out in the shop. The primary objective in cupola is to produce iron of desired composition, temperature and properties at the required rate in the most economical manner. Besides, this furnace has many distinct advantages over the other types, e.g., simplicity of operation, continuity of production, and increased output coupled with a high degree of efficiency. Description Of a Cupola : The Cupola Furnace consists of a vertical, cylindrical steel sheet, 6 to 12 mm thick, and lined inside with acid refractory bricks or acid tamping clay. The refractory bricks or the tamping clay used consist of silicon oxide acid (SiO2) and alumina (Al2O3). The lining is generally thicker in the lower where the temperatures encountered are higher than in the upper region. The shell is mounted either on a brick work fo...
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