Abstract
The traditional melting unit in cast iron foundries is being replaced by induction furnaces in high-quality foundries. Thermal efficiency, cost of equipment and melting costs has been overlooked due to quality and raw material problems. Some foundries have used technologically upgraded versions of the cupola with improvements in thermal efficiency and resultant cost savings and ecological considerations.
A review is of utmost importance in view of the changed circumstances of energy conservation and global warming, technological improvements in cupola design and practice, availability of better raw materials, pollution control, and modern developments. This paper presents the best possible estimates of thermal efficiency and elemental carbon consumed per unit weight of CI melted for different methods of cast iron melting. The carbon consumed is directly proportional to the main greenhouse gas, carbon dioxide, responsible for global warming. The findings can be used as a guide for judicious process selection.
Introduction
The traditional melting unit in cast iron foundries, the cupola has been/is being replaced by induction furnaces by high-quality, high-production mechanized foundries. All new foundries are also coming up with induction furnaces. The reasons have been
1.Lack of chemical composition control
2. Low pouring temperature
3. Air pollution and ecological considerations.
4. Final product quality (mechanical properties and casting defects assigned to cupola melting, often erroneously and without proper analysis).
5. Lack of availability of good quality coke (ash content and friability) and pig iron (Chemical consistency and high phosphorus content)
6. A mental block that induction furnace always produces better quality castings. This is definitely true for leakproof auto castings like cylinder blocks, heads, etc. which cannot tolerate phosphorus content above 0.08%. Due to the high phosphorus content (0.15 -0.4 %) of pig iron produced by our steel plants (the only source till recently) and widely varying carbon and silicon content, direct cupola metal cannot be used for these castings. Duplexing can take care of compositional adjustment and temperature but not phosphorus.
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