Preamble

In steelmaking, ladles are employed to transfer molten steel from BOF/EAF to ingot casting or continuous casting. It has been realized that ladles can be used very effectively as a reactor which can perform any of the following functions:

• To desulphurize molten steel tapped from BOF/EAF
• To homogenize molten steel to minimize gradients in concentration and temperature and to attain desired teeming temperature.
• To deoxidize molten steel
• To improve cleanliness of steel by removing inclusions
• To engineer the inclusions so as to alleviate their harmful effects on mechanical properties of steel
• To add alloying elements
• To remove dissolved gases

The effectiveness of each of the function requires modifying the ladle in terms of molten steel flow, and extra heating facility etc.

What modifications are required?

Ladle is a cylindrical refractory lined vessel and aspect ratio of the bath varies between 0.8 and 0.9. This means that the bath is deep.

Bath agitation would be required to carry-out the functions effectively. At high temperature, bath can be agitated either by an inert gas or by induction. One has to determine the amount of stirring gas and location of the injection of gas in the ladle. The gas can either be injected through the nozzle or porous plugs. Location of the injection elements is an important issue. Injection elements could be located either axis-symmetric or asymmetric to the center of the ladle.

Enough free board height in the ladle must be available to accommodate the quantity of slag required for refining and to absorb inclusions.

Additional heating may be required to keep the molten steel to the teeming temperature. This can be achieved either by tapping steel at slightly higher temperature or to provide addition heating arrangement in the ladle itself.

In many situations it is required to inject the slag forming materials either for refining or for inclusion engineering. In this case suitable injection device must also be available.

Above all, the most important would be the selection of refractory (see lecture 9 and 10) to meet the refining requirements. Refractory materials for injection elements and their fixing must also be considered.