In electric arc furnace design, the hearth refers to the lower section of the furnace that holds the molten steel during melting. This area plays a critical role in both metallurgical performance and structural integrity.
Hearth Shape and Geometry
Typically, the hearth is designed with a spherical bottom and a truncated conical melting zone. The spherical section at the base accounts for about 20% of the total molten steel depth. The conical walls form an angle of 45° with the vertical, facilitating efficient tapping and easier maintenance.
This geometry offers several key advantages:
- The spherical bottom promotes early steel collection during melting, offering better thermal protection to the refractory lining.
- The shape helps avoid direct contact between electric arcs and the hearth, improving refractory life.
- The sloped conical section ensures that the furnace can be tilted up to 40° for complete steel tapping and supports effective hot repairs.
Volume Calculation of the Molten Bath
The volume of molten steel in the hearth can be calculated using the formula:
V = M × V0
Where:
- V is the molten steel volume (m³)
- M is the furnace’s nominal capacity (tonnes)
- V0 is the specific volume of molten steel, typically 145 m³/t
The ratio between the molten steel surface diameter and its depth is usually in the range of 3.5 to 5.5, ensuring optimal melting behavior.
