The tundish design fundamentals are based on the idea of steady-state operation rather than transitional, or nonsteady-state operations. The primary functions of the tundish are to act as a buffer reservoir between the ladle and the mold but nowadays its functions have been broadly diversified which includes effective inclusion removal, thermal equilibration, chemical homogenization, and to provide a nonreactive environment and as a container vessel that supports the kinetics and thermodynamics of these functions.
Thus designing of tundish is critical in order for the tundish to be used as an inclusion, temperature and chemistry refiner and serve as the noncontaminator vessel.
The tundish design has to be constructed keeping in mind the fundamental and metallurgical need of the steelmakers and these are some of the points to ponder upon:
• The product which is to be casted.
• Matching the number of strands.
• Cleanliness improvements.
• Lining thickness and design.
• Need for latest tundish furniture.
• Tundish fly capability and the need for extended continuous casting.
• Yield losses.
The need for improvement in steel cleanliness remains the key and of utmost priority. Thus design has to be constructed keeping in mind the cleanliness essentials of tundish whereas tundish size is defined by its wall angles and the length, height and width dimensions, while geometry is often determined by the number of strands to be cast, as well as by available shop floor layout constraints.
Examples of various tundish shapes are boat type, T-type, V- type, C-type and H- type.
The trough-shaped tundish, commonly known as a boat- or bathtub-shape, is probably the most frequently encountered design.
Variations of the rectangular-base trough include coffin-shaped and flared-trough designs. The trough shape is one of the common design in single- and two-strand slab casters, and can also be found on many bloom and billet casters.
The V-shaped tundish has a huge pouring box and a more circuitous path to the strand as compared to a conventional trough tundish.
The C-tundish is a modified version of the boat- and V tundishes shapes taken into combination .
The T-shaped tundish is employed on bloom/billet machines and is essentially a modified trough with a separate and contain a central pouring box. The design inhibits the turbulence in the pouring box to spread to the inner strands and ensures a full metal head for delivery to all strands eliminating the chances of strand failures.
Numerical investigation of Boat shape, T-shape and V-shape tundishes have been carried out by solving the Navier-Stokes equation together with the standard k-ε turbulence model. Mixing phenomena has been studied numerically by solving the species concentration equation. The residence time distribution (RTD) curves have been used to analyze the intermixing amount inside the different shapes of tundishes. Velocity vectors of molten steel have been predicted and comparative study of fluid flow and intermixing have been performed for different cases. A numerical model has been validated with the experimental result obtained from the water model setup of the continuous casting tundish. Studies have shown that the shape of tundish plays a significant role in the intermixing amount. V-shape tundish has been found to have the least amount of intermixing as compared to that of Boat and T-shape tundish of steel during ladle change over.
Fluid flow in tundish shows that turbulence in the molten steel flow increases the intermix amount. Effect of tundish shape and outlet position have a significant effect on the production of steel of different grade specifications as well as reduce short-circuiting issues.
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