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Casting

Entrapment of non-metallic inclusions   1 of 3
 
The final stage of steelmaking is casting. Refractory shrouds are used during casting to prevent atmospheric exposure and therefore allow reactions to occur between oxygen and alloying elements in the molten steel resulting in inclusions being formed. Other practices are also used during casting which actively promote the removal of inclusions from the steel, thereby improving steel cleanness:

Electromagnetic slag detection in the exit port from the steelmaking ladle is used to prevent ladle top slag being carried over into the tundish and entrained in the inclusion population; as the steel level in the ladle falls during casting, there is a chance of ladle top slag being entrained in the steel flow through the exit port. If this happens the magnetic flux measured by detector coils changes and sends as signal which shuts off the steel flow from the ladle.

'Tundish Furniture' is used to generate steel flows in the caster tundish which promote inclusion removal to the tundish powder layer, with a steel cleaning effect; dams and weirs are commonly used to set up steel flows across the steel / tundish powder interface. By doing this, the distance which an inclusion must travel to float out of the steel and be captured in the tundish powder is reduced, thereby promoting steel cleaning.

Flow from the tundish to the mould is controlled via a stopper rod or sliding gate mechanism which is linked to the metal lever detector in the mould. This stream is also shrouded by a refractory tube which is carefully designed to optimise flow conditions in the mould and promote conditions for any further inclusion flotation.

Have a go!Select different liquid steel feed rates to the tundish from the ladle to investigate the effect on the possibility of generating non-metallic inclusions in the final steel product.

  • The results of sampling at different pouring speeds can be copied and pasted into spreadsheet applications.
  • The micros are generated from the calculated size distributions -  they provide a good visualization of the importance of pouring speed.
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